BEIJING - He's back.

Tyson Gay passed his first-round qualifying test Friday morning in the men's 100-meter dash at Olympic Stadium, familiarly known as The Bird's Nest.

Gay, testing his left hamstring for the first time in competition since straining it at last month's U.S. Trials, won his heat in 10.22 seconds.

Co-favorite Jamaican standouts Usain Bolt and Asafa Powell easily won their heats, as did countryman Michael Frater.

The top three finishers in each of 10 heats, plus the next 10 fastest finishers, advanced to the quarterfinals (scheduled for Friday night Beijing, Friday morning U.S.).

Gay, the reigning world champion at 100 and 200 meters, set an American record of 9.77 at the U.S. Trials, and later ran the fastest 100 of all time, a wind-aided 9.68. But he made it through only one round of the 200 before tumbling to the track early in his quarterfinals heat.

"A little sluggish," Gay said after Friday's race, "but my body's awake now."

His said his hamstring "felt fine."

Second and third in Gay's heat, both time in 10.29, were Olusoji Fasuba of Nigeria and Jose Carlos Moreira of Brazil.

Bolt, the world record-holder at 9.72, got things going in the first heat. Barely breaking a sweat, Bolt loped easily to a win in 10.20. Runner-up Daniel Bailey clocked 10.24.

Powell, who had the world record (9.74) until Bolt bettered it May 31, was a little more business-like in his approach to the second heat, then eased the last 20 meters. His heat victory came in 10.16, followed by 2004 Olympics finalist Kim Collins of St. Kitts and Nevis in 10.17.

Other winners of early heats included Trinidad and Tobago's Richard Thompson (10.24) and Frater (10.15).

Reese Hoffa was first to automatically qualify for finals of the men's shot put, popping 66 feet, 11½ inches on his only attempt. Teammates Adam Nelson (67-5 ½) and Christian Cantwell (67-2 ¼) also advanced.