World champion Tyson Gay fell in the curve of his 2 0 0 - m e t r e quarterfinal heat Saturday at the US OlympicTrack and Field Trials, ending his bid for a 100-200 double at the Beijing Olympits.

Gay, who last weekend ran the fastest 100 under any conditions in a wind-aided 9.68 seconds to win the final, tumbled to the track with a possible hamstring injury that could mean he would miss out on the Olympics altogether.

Gay, who won the 100 and 200 at last year's worlds, was in lane seven in the first heat of the 200 quarterfinal. He sped out of the blocks but within a few steps went down to the amazement of more than 20,000 at Hayward Field.

He was helped off the track but it was not immediately . known how severe |hc injury that sent him tumbling to the track had been.

At the very least, it doomed Gay's dream of a golden sprint double next month at Beijing. Only the three top finishers in Sunday's 200 final will run in the event for the American team at the Olympics.

An Olympic dream also died for 1996 Olympic 110 hurdles champion Allen Johnson, who at 37 was bidding for a fourth Olympics but pulled up after the fourth hurdle of his 110 hurdles qualifying heat.

Johnson said he injured a tendon in his left leg six weeks ago.

"I knew this was a possibility," Johnson said. *1 hoped that it wouldn't happen, but it just didn't hold up. After the first hurdle, as I kept going, the pain just got progressively worse. This is really disappointing for me.”

Reigning Olympic 200 champion Shawn Crawford led semifinalists in the event in 20.33 seconds with Walter Dix, a 100 Olympian, second in 20.56.

Wallace Spearmon, Xavier Carter and John Capel were also among 16 to advance after Gay's stunning collapse.

Two-time women’s world 200 champion Allyson Felix eased up 40 meters from the finish and settled for second in her 200 quarter-final heat, in 23.09. matching lOOin Olympian,Torri Edwards for eighth fastest of 16to advance.

Felix finished with the 100 final and will not going for a 100-200 sweep at Beijing either, although Edwards, 100 winner Muna Lee and 100 qualifier Lauryn Williams all remain in 200 contention.

Shalonda Solomon led semifinalists in 22.68 with Marshevet Hooker next in 22.74

David Oliver, a May winner at Doha in 1255, won his heal in 1324 seconds to lead all 1 lOhurdlesqualifiers.

Two-time Olympic runner-up and 2007 world runner-up Terrence Trammell was second in his heat in 13.50 while David Payne, third at last year's worlds, was second in his heat in 13.39.

Women's world indoor 60m hurdles champion Lolo Jones had the fastest time in 100 hurdles qualifying, winning her heat in 12.68 with 2004 Olympic champion Joanna Hayes second in the heat and overall in 12.74.

Damu Cherry, who missed the 2004 trials while on a two-year doping ban, won her heat in 12.92. The 30-year-old has this year's fastest time in the world this year, a 12.47 run in May.

Two-time world champion Michelle Perry, who resumed training six weeks ago after a hamstring injury, advanced imiXU/ Only three runners were eliminated in the round.

Quarterfinals in the hurdles and 200 semi-finals were to be staged later Saturday with finals in both set for Sunday. Finals later Saturday include the high jump, where 2004 Olympic champion Dwight Phillips bids for a Beijing trip.