A man has been arrested after a bottle was thrown on to the track at the start of the men's 100m final at the Olympic Stadium, the Metropolitan Police said.
A police spokesman said a man had been heard shouting abuse and was then seen throwing a bottle immediately before the race, won by Jamaican sprinter Usain Bolt.
Speaking after the race, US sprinter Justin Gatlin, who won bronze, said: "It was a little distraction and I didn't know what it was. But when you're in those blocks and the whole stadium's quiet you can hear a pin drop."
Bolt told reporters he had been unaware of the incident. He added: "No, I keep hearing that. I don't know who would have done that."
Fellow Jamaican sprinter Yohan Blake said: "I was so focused I didn't see anything. I was so focused on just running to the line."
Edith Bosch, Holland's world judo champion, claimed on Twitter that she had "beaten" the person who had thrown the bottle.
She said: "A drunken spectator threw a bottle onto the track! I HAVE BEATEN HIM .... unbelievable."
Nobody was injured during the incident and the event was not disrupted, police said.
The suspect is being held in police custody at an east London police station on suspicion of causing a public nuisance.
Gatlin said the incident had not affected the race: "You just have to block it out and go out there and do what you got to do. You can't complains about that, the race went on and it was a great race."