American Aaron Peirsol (search) reclaimed the gold medal in the Olympic 200-meter backstroke after initially being disqualified for what an official called an illegal turn Thursday night. The United States filed a protest that was overturned on appeal by FINA, the sport's governing body, about 30 minutes after the race — just before the medal ceremony was held.

FINA officials said the decision was reversed because the judge in Peirsol's lane provided inadequate details about the alleged violation that were "not in the working language of FINA."

Meanwhile, American Michael Phelps (search) won his fourth gold medal of the Olympics in the 200-meter individual medley Thursday night, leading the entire race. Phelps finished in an Olympic-record time of 1 minute, 57.14 seconds, lowering his own mark of 1:58.52 set in the semifinals one night earlier.

Ryan Lochte of Daytona Beach, Fla., earned silver in 1:58.78. George Bovell of Trinidad took bronze in 1:58.80.

Peirsol, the world record-holder and current world champion, led most of the backstroke race and easily beat the field, touching first in 1 minute, 54.95 seconds. He was more than two seconds ahead of the next swimmer, Austria's Marcus Rogan.

Peirsol clutched a lane rope and held up his right index finger, thinking he had become the fifth swimmer to sweep both backstroke events at the Olympics, after already winning gold in the 100.

But there was a delay in putting up the official results. After several minutes, the scoreboard flashed "DSQ" beside Peirsol's name — a disqualification. The crowd gasped and then began to boo. Still standing on deck, the 21-year-old from Irvine, Calif., shrugged his shoulders in disbelief.

"It sounds pretty bogus to me," he said. "I think I got disqualified for crossing the lane line before people had finished, but I'm not sure."

Coincidentally, Peirsol stirred controversy earlier in the meet when he accused Japan's Kosuke Kitajima of doing an illegal dolphin kick while winning the 100 breaststroke. Swimming officials found nothing wrong with Kitajima's technique, and he completed a sweep of the breaststroke events in the 200 Wednesday night.

Rogan wound up with silver in 1:57.35, while Romania's Razvan Florea settled for bronze (1:57.56). Great Britain's James Goddard, who initially had a bronze, dropped back to fourth in 1:57.76.

Goddard was second much off the race, only to get passed by Rogan and Florea on the final leg. He said he didn't know what happened in Peirsol's lane.

"You can hear the crowd and they are not happy," he said. "There should be a way on the scoreboard so people know why there is a disqualification."

Peirsol won the 100 back Monday and duplicated teammate Lenny Krayzelburg's sweep of the backstroke events in 2000. At the Sydney Games, Peirsol gave a glimpse of his potential by winning silver in the 200.