Rio police have tried to stop American swimmers James Feigen and Ryan Lochte from leaving Brazil in order to question them further about a disputed robbery that took place on Sunday morning.
United States Olympic Committee (USOC) spokesman Patrick Sandusky said local police came to the athletes' village on Wednesday morning to meet the pair and seize their passports.
But Sandusky added that "we were not able to make the athletes available" as the swimming team moved out of the village when their competition ended last weekend.
Lochte's social media accounts suggest he is back in the United States but Feigen's whereabouts are unknown.
"As part of our standard security protocol, we do not make athlete travel plans public and therefore cannot confirm the athletes' current location," said Sandusky.
This new development is just the latest in a bizarre story that began when reports emerged the morning after Lochte's last swim in Rio that he had been robbed at gunpoint.
This was initially denied by USOC, despite Lochte's mother telling American media that she had heard it directly from her son.
The story changed later on Sunday when Lochte told US TV that he, Feigen and two other American swimmers, Gunnar Bentz and Jack Conger, were travelling back to the athletes' village from a party when their taxi was stopped by armed men posing as military police and they were robbed.
The 26-year-old Feigen won a gold medal in the men's 4×100 metres freestyle relay, while Lochte, 32, won his 12th Olympic medal, and sixth gold, in the 4x200m relay.