Police in Rio de Janeiro, Brazil, said Tuesday they have been unable to verify claims U.S. Olympian Rio Lochte and three other swimmers were robbed at gunpoint over the weekend.

A police official familiar with the investigation told the Associated Press detectives have not been able to get in touch with the cab driver or witnesses of the armed robbery, prompting concern the Americans' claims may be untrue.

"This happened the way he described it," Lochte's attorney, Jeff Ostrow, told AP. "It doesn't behoove Ryan and anyone else to make up a story."

Lochte left a party at the French Olympic team's hospitality house with Gunnar Bentz, Jack Conger and Jimmy Feigen overnight Saturday. The four men had taken a taxi home, but say they were mugged by a group of fake police officers at an unofficial checkpoint.

"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," Lochte said on NBC's "Today Show" the following day. "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," Lochte added.

The group has been on the defensive since the attack for not immediately reporting the incident to police. Lochte and another unnamed swimmer told police they had been intoxicated at the time of the event and could not pinpoint details of the incident, including the color of the cab or the specific address of the run-in.

The four U.S. swimmers will continue to be treated as victims of a crime despite the lack of evidence police say they have uncovered surrounding the robbery. Police in Rio said they encounter dozens of robberies a day in the city, especially during the Olympics when tourists are targeted.