Dominican Republic ? The United States lost two gold medals at the Pan American Games 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 would 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. Sunday, Suriname’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.

Tara Nott of Stilwell 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.

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 accept 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 452/3.