Claims and denials
• Ryan Lochte says he did not have his wallet with him when he went through security at the athletes' village.
• Footage of him at the security check showed him with an object in his hand - which he claims was his cellphone.
• Lochte told police the US swimmers hailed a cab from the Ipiranga service station.
• The manager has told Rio reporters the group was never there.
Three US Olympic swimmers were dramatically stopped from leaving Brazil on Wednesday night as Ryan Lochte again changed his story about the armed robbery he claims the four went through in Rio over the weekend.
The US Olympic Committee confirmed that Jack Conger, 21, and Gunnar Bentz, 20, were removed from their return flight to the US and detained as the situation involving them and 32-year-old Lochte threatens to escalate into a full-blown international incident.
The USOC also confirmed that Jimmy Feigen, 26 - the fourth member of the ill-fated party last weekend - was also prevented from leaving Brazil and held.
Earlier on Wednesday, Lochte and Feigen were barred from leaving Brazil - but Lochte had already left - as police in Brazil say their accounts do not match security footage.
The action comes amid increasing tension between Brazilian authorities and the American swimmers - pitting the reputations of the Rio authorities and Olympic Games against their story.
On NBC, Lochte repeated his claim they were robbed but changed certain, crucial elements - while 8000km away his younger teammates were being held at a police station.
Lochte and his three teammates said they were held up at gunpoint in a taxi and had their wallets stolen as they returned to the athletes village from a night out, several hours after the last Olympic swimming events were held.
Police have found little evidence so far to support their accounts, and security video shows them returning to the Olympic village seemingly unfazed by their experience and still in possession of their valuables.
NBC reported that Lochte backed off some of his earlier claims. He now says the taxi wasn't pulled over but that they were robbed after making a stop at a gas station.
He also said the assailant pointed a gun at him rather than putting it to his head.
Lochte said in a telephone interview that he was not told by anyone in Brazil to remain in the country but said he would co-operate.
NBC host Matt Lauer gave Lochte a chance to address speculation the entire armed robbery story was fabricated to cover up for another possible nefarious activity - possibly with someone they wouldn't want to be associated with.
Lochte strongly denied this and said it was absolutely not the case.
"I wouldn't make up a story like this nor would the others - as a matter of fact we all feel it makes us look bad," said Lauer, quoting Lochte. "We're victims in this and we're happy that we're safe."
The DailyMail.com website reported that sources said Lochte was adamant that he did not have his wallet with him when he went through security at the athletes' village.
However, footage of him at the security check showed him with an object in his hand - which he claims was his cellphone.
USOC spokesman Patrick Sandusky said that swimmers "Jack Conger and Gunnar Bentz were removed from their flight to the United States by Brazilian authorities. We are gathering further information".
A police source said Feigen had been detained by police before he boarded the plane, Reuters reports.
Feigen checked in for a flight online but never showed up.
Sources told NBC that authorities did not want to hold the Olympic swimmers long, but want to ask them exactly what happened on the night of the alleged robbery.