DENVER -- Denver Broncos safety Lee Flowers was suspended without pay for the first four games of the regular season for violating the NFL's banned substances policy.

Flowers said he tested positive for ephedra, an over-the-counter stimulant that speeds the heart rate and constricts blood vessels, but wasn't aware the supplement was in his system. He said his positive test stemmed from a vitamin he took in December.

"Unfortunately, that vitamin had ephedra in it," Flowers said Saturday. "I'm a little disappointed in myself because I did everything that's possible to take precautions and try not to put quote, illegal, substances in my body, but it is what it is."

The NFL banned ephedra after the death of Minnesota Vikings offensive tackle Korey Stringer during training camp in 2001. Players are tested and can be suspended after the first violation, as Carolina rookie Julius Peppers was for the final four games of last season after he tested positive for the supplement.

The league is looking into using one authorized supplier for dietary supplements because several players have said they took ephedra without knowing it, including Peppers and Flowers.

"Right now, this thing just caught the whole league off-guard," Flowers said. "They don't know what to do. The players don't know what to do. We've just got to be careful."

Flowers said he appealed the suspension, but lost a hearing in June. He also criticized the league's drug policy.

"I would have been better off smoking crack. I would have got a slap on the wrist," Flowers said. "And that's a shame because here's something where we don't know what's going into these vitamins, but I can go out here and smoke crack and it's like, 'Well, you be careful next time.'"

Flowers also said his lawyers are contemplating legal action against supplement companies for not listing all of the ingredients in their products.

Flowers will be able to participate in training camp and Denver's four preseason games before his ban starts Aug. 31. He will be eligible to return to the active roster after Denver's game against Detroit on Sept. 29.

Broncos coach Mike Shanahan said the team signed Flowers in June knowing he would be suspended.

"We brought him in and liked him anyhow," Shanahan said. "And when he did come around, he came in and we had talked about it and told me what happened. I felt good enough to sign him."

Flowers signed a one-year deal with the Broncos after spending his first eight seasons with the Pittsburgh Steelers, including the past five as a starter. He started 14 games and had 73 tackles last season.

Flowers is expected to compete for playing time with free safety Sam Brandon and strong safety Kenoy Kennedy, the projected starters.

Earlier this week, Food and Drug Administration Commissioner Mark McClellan told Congress the government is building a case that could lead to banning ephedra.

The FDA in February ordered labels to be put on products with ephedra warning of the possibility of heart attacks, strokes or death. The move came two weeks after the death of 23-year-old Baltimore Orioles pitcher Steve Bechler, who was taking a supplement containing ephedra.

Under pointed questioning from House members, McClellan said the agency is looking at taking stiffer action.