Brazilian police pulled two US Olympic swimmers off a plane about to leave the country to question them about a claim they made to have been victims of an armed mugging, according to US officials.

"We can confirm that Jack Conger and Gunnar Bentz were removed from their flight to the United States by Brazilian authorities," Patrick Sandusky, spokesman for the US Olympic Committee, said on Wednesday.

Conger and Bentz were with star US swimmer Ryan Lochte and another squad member, James Feigen, when they said they were robbed at gunpoint on Sunday. Lochte is believed to be already in the US, having left before Brazilian authorities ordered the swimmers be questioned.

It was not yet clear if Feigen was still in Brazil or in the US.

Both Conger and Bentz were released from police custody early on Thursday after questioning, but their lawyer said they were not allowed to leave the country until an investigation was completed.

READ MORE: US swimmer Ryan Lochte robbed at gunpoint

Later on Thursday, reports emerged that the US swimmers had been involved in a fight with an armed gas station security guard on the night in question.

The unconfirmed reports on ABC News and Brazil's G1 news site said an altercation occurred when the swimmers had been out partying and that the incident was caught on security camera footage.

G1 quoted Rio police saying that the athletes had stopped at the gas station in a taxi to use the bathroom. When they damaged the bathroom door, a security guard pulled out his weapon and made them stay until police arrived, prompting a confrontation, G1 reported.

ABC quoted an unidentified Brazilian police source saying CCTV footage shows a swimmer "breaking down the door to the bathroom at the gas station and fighting with a security guard."

Some Brazilian officials have suggested that the swimmers may have made up their account of the mugging and could face charges for filing a false report, a serious crime in Brazil.

"Bents and Conger boarded a flight here in Rio International Airport on Wednesday, but before the flight could leave for the US, federal police boarded the plane, took these two athletes out of the plane, and detained both of them and took both of their passports,"  Al Jazeera's Gabriel Elizondo, reporting from Rio, said. 

US swimmers could face charges for filing a false report [Globo TV/ Reuters]

"These four Olympic swimmers left a party early on Sunday," said Elizondo. "They were on their way back to the Olympic Village in a taxi ... they all say that they were robbed at gunpoint on the side of the road." 

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"They claim that perhaps the people robbed them at gunpoint were wearing police uniforms. A very, very serious claim by these four athletes."

At first, the International Olympic Committee denied that anything had happened.

Lochte, though, gave interviews in which he described the incident in detail and Brazilian Olympic authorities were eventually forced to issue a public apology for the security slip-up.

But, early on Wednesday, a Brazilian judge ordered an investigation saying their story was "full of inconsistencies".

Judge Keyla Blank "issued warrants for searches and the seizure of the passports for the US swimmers", a statement from her office said.

"With this, they are banned from leaving the country."

Blank's office said the judge was investigating possible inconsistencies in the swimmers stories, including different accounts of how many muggers there were. Olympic officials said police were still looking for key witnesses, including the driver of the taxi the swimmers said they were in.

'Touched a nerve'

The judge also referenced footage caught on security cameras after the alleged robbery.

"It's noticeable that the victims arrived back physically and mentally unshaken, even joking with each other," the judge said.

"In the last 48 hours some video came to light. It shows these athletes arriving in the village after the alleged robbery took place," said Elizondo. "They seem to have their cell phones, wallets. They seem to be joking with each other. That resulted in people asking if a robbery really took place or not." 

The video in question, posted on the website of Britain's Daily Mail, shows the four swimmers passing through an X-ray machine in the early hours of Sunday. The clip shows nothing out of the ordinary.

With some 85,000 police and soldiers guarding the Olympics - twice the number used in London - the apparently high-profile crime touched a nerve in Rio.

In addition to multiple incidents of thefts from Olympic athletes or media, a Portuguese government minister was recently mugged in the Leblon district.

Lochte, 32, won gold in Wednesday's 4x200 freestyle relay   [Jason Getz/USA TODAY Sports]

Source: Al Jazeera And Agencies