The Brazilian authorities have stopped US swimmers Gunnar Bentz and Jack Conger from boarding a flight at Rio de Janeiro airport, the US Olympic Committee has confirmed.
The two men were taken off a plane, bound for the US, for questioning late on Wednesday and released hours later.
Two teammates – Ryan Lochte and James Feigen – were barred from leaving the country, but Lochte has already left.
Police have queried their accounts of a robbery they reported in Rio on Sunday.
The four swimmers said they had been robbed at gunpoint in a taxi in Rio in the early hours.
Lochte is one of the most successful swimmers in history, with 12 Olympic medals, and he once had his own reality television show in the US. In Rio, he swam in two events, winning gold in the 4x200m freestyle relay.
Feigen, who told the San Antonio Express he was still in Brazil, won gold in the 4x100m freestyle relay.
Bentz competed in the 4x200m preliminaries, but not the final. He still received a gold medal after the US team’s win.
What has been the reaction to the arrests?
A statement from the US Olympic team said that Bentz and Conger “were released by local authorities with the understanding that they would continue their discussions about the incident on Thursday”.
“James Feigen is also communicating with local authorities and intends to make further statements regarding the incident on Thursday as well,” said TeamUSA.
Lochte’s lawyer told the BBC he had returned to the US two days ago.
“He arrived back before the judge issued anything,” said Jeffrey Ostrow.
“He was never asked to remain for further investigation or for any other purpose after he met with Brazilian authorities after he gave a statement.”
What do we know of the alleged robbery?
Accounts of what happened to the swimmers have been confusing from the beginning, and it appears they did not immediately alert either the Brazilian police or the Olympic authorities about it.
News of the incident emerged after Lochte’s mother told US media about it.
Lochte himself gave an initial account of the events to US TV network NBC on Sunday, saying he and the other swimmers were in a taxi returning from a club in the early hours when they were pulled over by men wearing police badges.
He said they pulled a gun and told the swimmers to get on the ground. “I refused… and then the guy pulled out his gun, he cocked it, put it to my forehead…”
Lochte has since slightly altered his account, telling NBC on Wednesday that the taxi was not pulled over – they were robbed while making a stop at a petrol station – and says the gun was not pointed directly at his forehead.
He called the inconsistencies a “traumatic mischaracterisation” caused by the stress of the incident.
What has been the Brazilian authorities’ reaction?
The judge investigating the case found further inconsistencies and ordered police on Wednesday to seize the swimmers’ passports to prevent them leaving Brazil.
Police say they have not been able to track down the driver who the swimmers said drove them back to the village.
And CCTV footage of their return to the athletes’ village appears to show the swimmers laughing and joking, and handing over their wallets, phones and accreditation, as they go through the security screens. The judge said they did not show signs of being affected by a robbery.