The party featured electronic house music, he said, and the group had attended to celebrate another swimmer’s birthday. He said the Americans had left around 3 a.m.

Sppezapria distanced the party from the episode, saying that a police car had been stationed outside Club France all night. “It sounds like a rough situation,” he said. “But it didn’t happen here.”

The civil police in the state of Rio said they were investigating. One of the swimmers had spoken with the police, they said, and given a report of the episode. That swimmer, who was not named by the civil police, said he and his teammates were in a taxi when they were stopped and held up. He told the police he did not know precisely where the robbery took place.

The civil police said the other swimmers would be asked to provide separate accounts. The police were also trying to track down the taxi driver.

Bentz, one of the swimmers who was robbed, declined to comment when reached by The New York Times on Sunday. Lochte initially denied reports of the robbery through Olympic officials.

He later told NBC News that one of the men had put a cocked gun to his head.

“We got pulled over, in the taxi, and these guys came out with a badge, a police badge — no lights, no nothing, just a police badge — and they pulled us over,” he said. “They pulled out their guns, they told the other swimmers to get down on the ground — they got down on the ground. I refused — I was like, we didn’t do anything wrong, so — I’m not getting down on the ground. “And then the guy pulled out his gun, he cocked it, put it to my forehead, and he said, ‘Get down,’ and I put my hands up. I was like, whatever. He took our money, he took my wallet — he left my cellphone, he left my credentials.”

“I think they’re all shaken up,” Ileana Lochte, the swimmer’s mother, told USA Today. “They just took their wallets, and basically that was it.”

Bentz and Conger participated in the heats of the 4x200-meter freestyle relay, but not the final. Feigen did the same in the 4x100-meter relay.