RIO DE JANEIRO – Allegations that star US swimmer Ryan Lochte invented a story about him and three team mates being mugged at gunpoint in Rio strengthened on Thursday (Aug 18) with video footage showing them in a gas station altercation.

The controversy took a dramatic new twist after the leaking of security camera footage from a gas station on Brazil's Globo television. This came hours after two of the swimmers were hauled off a plane about to leave Rio de Janeiro for the United States and taken in for questioning.

The video footage appears to support police accusations that the medal-winning swimmers vandalised a gas station bathroom where they had stopped off after all-night partying. They were then detained by a security guard.

The four swimmers are seen in the video getting out of a taxi after a man identified as the security guard approaches. Later they are seen being made to sit on the ground.

Brazil's G1 site quoted police saying the athletes broke the gas station's bathroom door and started a confrontation with the armed security guard, who pulled out his weapon and made them wait for police to arrive.

This version of events is a far cry from 32-year-old Lochte's claims.

The swimmer, one of the most visible faces of the Olympics and winner of six gold medals, told media that the four had been robbed at gunpoint by a man claiming to be a policeman.

His report caused the Olympic authorities huge embarrassment, highlighting security worries at an Olympics where Brazil has deployed 85,000 police and soldiers – double the number used in the 2012 London Games.

However, the authorities soon raised doubts over the veracity of the allegation and the swimmers could face charges of filing a false claim with police.

A judge on Wednesday ordered the swimmers to be detained and their passports confiscated.

Lochte had already flown back to the United States. However, two other athletes -- Jack Conger and Gunnar Bentz – were removed by police from a plane just about to take off late Wednesday.

The fourth, James Feigen, was also still in Brazil.

"The three US Olympic swimmers... are cooperating with authorities and in the process of scheduling a time and place today to provide further statements to the Brazilian authorities," said Patrick Sandusky, spokesman for the US Olympic Committee.

INTERNATIONAL SCANDAL

The scandal overshadowed sporting action in the second week of South America's first Olympics, coming simultaneously with the arrest in Rio of IOC member Patrick Hickey on allegations of taking part in a black market ticket ring.

Hickey, who fell ill during his arrest on Wednesday, was expected to face interrogation once he is released from hospital.

Lochte's harrowing story got worldwide attention and touched a nerve in Rio, where violent crime is common.

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

On Thursday, British Olympic officials confirmed that an athlete had been robbed while returning to the Olympic Village, but was "safe and well."

The Guardian newspaper reported that British athletes had been warned not to leave the village complex for their safety.

Lochte's story was particularly alarming because it supposedly involved police or someone claiming to be police.

He described in detail how the assailant had a gun put to his forehead after the swimmers' taxi was pulled over by criminals who forced them to lie on the ground and stole money and other items.

"The guy pulled out his gun, he cocked it, put it to my forehead and he said, 'Get down,'" Lochte recounted. "He took our money, he took my wallet – he left my cell phone, he left my credentials." AFP