SAN FRANCISCO -- Big names in American sports continue to be called to testify in the ongoing federal grand jury investigation into a Burlingame, Calif. nutritional supplement laboratory and the designer steroid Tetrahydrogestrinone (THG).

Seven current or former Oakland Raiders are among 10 NFL players subpoenaed to testify, CBS Sports reported Sunday on "The NFL Today."

Two Oakland players confirmed Monday they have been subpoenaed.

Defensive tackle Dana Stubblefield said he was subpoenaed "a while ago," but doesn't know exactly when he will be in court. Running back Tyrone Wheatley also said he was subpoenaed in the case involving the Bay Area Laboratory Co-Operative, or BALCO.

"I didn't do nothing wrong," Stubblefield said. "It's something you've got to deal with, I guess."

Wheatley wouldn't elaborate about the BALCO investigation, saying only that his dealings with the lab are strictly "workout related."

"You all know my policy -- if it's not football related, I'm not going to talk about it," he said.

In the past two weeks several other prominent American athletes have been subpoenaed to testify, among them Major League Baseball's Barry Bonds and Jason Giambi. World sprint champion Kelli White, U.S. shot put champ Kevin Toth, and dozens of other Olympic and professional athletes have been called to testify.

What is THG?

Tetrahydrogestrinone is a specially designed anabolic steroid that has been tweaked by chemists to make it undetectable under normal testing. A high-profile coach sent a syringe of THG to the United States Anti-Doping Agency who have now developed a test for the previously undetectable drug. Anabolic steroids stimulate the muscle and bone cells to make new protein. They increase muscle strength and encourage new muscle growth, duplicating the effects of the male sex hormone testosterone, thereby allowing the athlete to train harder for longer periods of time. They increase aggression and competitiveness, enhancing muscle strength, size and power (the androgenic effect). Anabolic steroids are legally used in the medical profession for conditions such as osteoporosis, some forms of anemia (because they stimulate blood cell production) and to promote the recovery process after major surgery and serious illness. There is little evidence to suggest that using anabolic steroids alone promotes an increase in muscle strength in adult males with development due to appropriate diet and exercise. Because anabolic steroids mimic hormones already in the body, they can create an imbalance with the normal hormone balance. This can lead to side effects such as development of male features in women, loss of fertility, impotence, acne and kidney damage. -- Reuters

Along with Stubblefield and Wheatley, the other NFL players named were current Raiders linebacker Bill Romanowski, center Barret Robbins, defensive tackle Chris Cooper, fullback Chris Hetherington and former defensive end Josh Taves.

Of those, Romanowski, Robbins, Wheatley, Cooper and Taves were named in documents seized during a Sept. 3 raid on the Bay Area Laboratory Co-Operative (BALCO), a source familiar with the results of the search told The San Francisco Chronicle. The source said the documents listed several athletes who had received blood and urine testing through the company.

Romanowski's attorney, Harvey Steinberg, contradicted the reports and told ESPN's Andrea Kremer that Romanowski has not been subpoenaed.

Raiders coach Bill Callahan said he was aware several of his players were subpoenaed. He hasn't talked to them and doesn't plan to, saying he'd let authorities handle it.

"Absolutely it could be a distraction," Callahan said. "How it'll all play out and how the situations evolve, I don't know."

Chiefs wide receiver Johnnie Morton, Patriots linebacker Larry Izzo and Falcons linebacker Artie Ulmer -- who played with the 49ers in 2000 -- also have been called to testify, according to CBS Sports.

The network said that once the league learned of the subpoenas, it tested the 10 players for the designer steroid THG. A positive test for a first-time NFL offender earns a four-game suspension.

San Francisco Giants slugger Barry Bonds will testify in December. His attorney, Mike Rains, said last Tuesday that the San Francisco Giants' slugger had received a subpoena about a month ago asking him to appear Dec. 4.

Rains said he was told by a prosecutor that "Barry is a witness and not a target of the grand jury."

"It doesn't make great sense to be subpoenaing athletes of the caliber of Barry Bonds, just to drag them in so the jury can see them, if he doesn't have anything else to offer," Rains said Tuesday.

Rains also said that Bonds has never taken any steroids. He said that THG isn't on the list of illegal steroids and that the legislature may have to add it to the list before its use is illegal.

"They can run around and say this stuff's terrible, and it enhances performance," Rains said. "But the question is, have they banned it? If they haven't caught up with it, presumably it is still legal."

The company at the center of the investigation is the Bay Area Laboratory Co-Operative, or BALCO, which was raided by the Internal Revenue Service and local drug agents in September. An attorney for BALCO founder Victor Conte has confirmed his client is the target of the grand jury probe.

Conte's attorneys reiterated Tuesday that the lab founder is innocent, and noted that a grand jury probe is "a one-sided process" that includes only evidence presented by prosecutors.

The statement from attorneys Robert Holley and Troy Ellerman calls Conte "a scientist and businessman who has dedicated his life to helping others including high-profile athletes." It vows that BALCO's subsidiary, SNAC Systems, will continue to make and sell nutritional supplements such as the zinc-magnesium product ZMA.

Conte has estimated gross retail sales of ZMA during the past four years were about $100 million worldwide.

Meanwhile, Conte has been accused by the U.S. Anti-Doping Agency of supplying athletes with a new designer steroid -- tetrahydrogestrinone, or THG -- that is rocking the world of track and field.

On Wednesday, USA Track & Field proposed a new anti-doping plan that could substantially increase punishments and fines for athletes who use banned drugs, including possible lifetime bans for first steroid offenses.

The proposal was announced the same day a lawyer for British sprinter Dwain Chambers said the track star tested positive for the drug during an out-of-competition test Aug. 1 in Germany. Attorney Graham Shear said his client wasn't trying to cheat and was assured by Conte that the supplements he was given were within international rules.

Bonds has been a BALCO client since 2000, and in the June issue of Muscle & Fitness magazine credited Conte for a personalized program that includes nutritional supplements.

The home of Bonds' personal trainer, Greg Anderson, was raided last month in conjunction with the raid on Conte's lab.

"When Barry gets a grand jury subpoena and his trainer's door gets kicked in by drug enforcement agents, that's when I get involved," Rains told The Associated Press on Tuesday. "All of that has certain ominous appearances to anybody."

Conte has said in e-mails that he was told by athletes that 40 Olympic and professional athletes have been subpoenaed. Being subpoenaed does not imply any of the athletes has done anything wrong.

Conte was named by an unidentified track coach as the source of the substance that turned out to be THG, a previously undetectable steroid. Conte has denied he was the source.

The USADA said last week it retested hundreds of samples from track and field athletes after identifying THG, and that several tested positive during the U.S. track championships in June. Those athletes now face two-year suspensions.

On Tuesday, track and field's world governing body, the International Association of Athletics Federations, said it will retest about 400 urine samples from the World Championships. Any positive findings would lead to retroactive punishments.

The World Anti-Doping Agency said the test for THG has been sent to its accredited laboratories throughout the world. The test was developed by the anti-doping lab at UCLA, where the designer steroid was identified from a used syringe sent to the USADA.

"This sends a strong message that there will be no delay in catching those who cheat or who believe they can stay one step ahead of the system," said WADA Director General David Howman, who called on other such agencies to retest samples for THG.

On Wednesday, swimming's world governing body FINA said it would consider retesting drug samples from this summer's world championships for THG.

On Monday, NFL spokesman Greg Aiello said the league might retest its samples for THG. Major league baseball has said it will be unable to retest samples taken this year for THG, but plans to discuss whether to add it to the list of banned substances.

The IOC said Wednesday that detection of THG marked a breakthrough in anti-doping efforts and promised to "make all efforts" to test for the drug at next year's Athens Olympics.

"What is important is that anyone found not playing by the rules is aptly dealt with and that this serves to demonstrate that doping in sport will not be tolerated," the International Olympic Committee said in a statement.

Information from The Associated Press was used in this report.