SANTO DOMINGO, Dominican Republic -- The United States lost two gold medals at the Pan American Games on Tuesday after sprinter Mickey Grimes failed a doping test.

Hours later, the Americans swept all five swimming races. But Cuba won its ninth baseball championship, beating the United States 3-1.

Grimes was found to have excessive levels of ephedrine, a banned stimulant, and was stripped of his title in the 100-meter dash. He also led off the victorious 400-meter relay team that games officials said will lose its gold.

"I understand that athletes need to take responsibility for everything we put in our bodies,'' Grimes said in a statement released through the U.S. Olympic Committee. "I made a mistake and I know that my action carries with it a penalty.

"I sincerely regret letting down the U.S. delegation and my country, and I look forward to representing my country in the future.''

It was the second time in three days a gold medalist failed a doping test. On Sunday, Surinam's 800-meter winner Letitia Vriesde tested positive for excessive levels of caffeine and was stripped of her gold medal. Vriesde later admitted her guilt, games officials said.

An ephedrine positive carries a maximum penalty of disqualification from the meet and a public warning, but no suspension.

"USA Track & Field regrets Mickey Grimes' mistake,'' the federation said in a statement. "We have spoken to Mickey, and we feel assured that he had no intention of gaining any competitive advantage. Mickey is one of our top young athletes, and he has learned an important and difficult lesson from his error.''

Grimes, of Los Angeles, had 13.7 micrograms per milliliter of ephedrine in his system; the legal limit is 10.

Ephedrine, commonly found in over-the-counter dietary supplements and cold medications, is ephedra's active ingredient and is on the list of prohibited substances. Last month, the Food and Drug Administration said it was looking into banning ephedra, an herbal stimulant used to lose weight and boost athletic performance.

In February, the FDA 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 sudden death of 23-year-old Baltimore Orioles pitcher Steve Bechler, who had been taking a dietary supplement containing ephedra.

The United States swept the 100 dashes for the first time since 1987, when Lauryn Williams won the women's event and then Grimes took his race. Grimes won a world championships gold medal as part of the 2001 U.S. 400-meter relay team.

Also losing gold from the relay are Hason Smoots, Kenny Brokenburr and Olan Coleman. Brazil gets the gold.

The 100-meter title now goes to Jamaica's Michael Frater.

Americans collected lots more gold Tuesday night in the swimming pool, going 5-for-5. In all, the United States has 79 golds, 56 silvers and 51 bronzes for 186 medals. Cuba is next at 117: 56-30-31.

Robert Margalis (St. Petersburg, Fla.) won the 400-meter individual medley ahead of teammate Eric Donnelly (Gainesville, Fla.). Then Ben Michaelson (Seymour, Conn.) took the 100-meter butterfly, setting a Pan Ams record of 53.04 seconds.

In the women's 200 freestyle, Dana Vollmer (Fort Worth, Texas) had a big margin over Colleen Lanne (Tucson, Ariz.). And in the 200 breaststroke, Alexandra Spann (Austin, Texas) beat two Canadians.

Spann cramped so badly after the race she could not except her silver medal, so teammate Courtney Shealy stood in.

The United States capped the big night with a lopsided victory in the men's 800 freestyle relay, featuring Ryan Lochte (Daytona Beach, Fla.); Bryan Goldberg (Hollywood, Fla.); Jeff Lee (Muncie, Ind.) and Dan Ketchum (Cincinnati). They set a games record of 7:18.93.

"We're really pleased because that time would have been competitive at the last Olympics,'' said Ketchum, who won a silver medal in the 200 freestyle the previous night.

Ariel Pestano singled in the go-ahead run in the seventh inning, then homered in the ninth as Cuba continued its domination of baseball. Jered Weaver took his first loss of the summer and had his streak of scoreless innings end at 45 2/3.

The Cuban players stormed out of their dugout to mob their teammates after the final out, while the dejected Americans could do nothing but watch the celebrations.

"This is our gift to the Cuban people for all their support and inspiration they've given us since we've been here,'' Pestano said. "Viva Cuba!''

The Cubans dedicated the win to Cuban president Fidel Castro as an early birthday present. He turns 77 on Wednesday.

Americans went 3-2 in boxing.

Welterweight Juan McPherson (Cleveland) won his bout when Mexico's Alfredo Angulo Lopez retired. Heavyweight Devin Vargas (Toledo, Ohio) went down early, trailed 10-6 after one round, but came back in the following three rounds before stopping Brazil's Alexsandro Cardoso.

Super heavyweight Jason Estrada (Providence, R.I.) beat Sebastian Ceballo of Argentina, 26-8.

Flyweight Raul Martinez (San Antonio) lost to Juan Carlos Payano of the Dominican Republic. Martinez held a 2-1 lead after one round, and the bout stayed close until the end, when Payano landed two punches for an 18-17 victory.

Light welterweight Lamont Peterson (Washington D.C.) was easily beaten by Patriz Lopez of Venezuela, 23-8.

Tara Nott (Stillwell, Kan.) won gold in the 48-kilogram class. A former soccer player and gymnast, she won a gold medal in the Sydney Games in weightlifting, the first time the sport was held at the Olympics.

A gold in modern pentathlon for winner Vaho Iagorashvili (San Antonio) qualified him for the Athens Olympics.

The U.S. women were beaten by Uruguay 35-21 for the handball bronze medal.