The uproar has its origins in a lavish Olympics party hosted by the French authorities over the weekend at the Sociedade HÃpica, a riding club that is a bastion for Rioâs old-money elite. The four swimmers â Mr. Lochte, Jimmy Feigen, Jack Conger and Gunnar Bentz â stumbled out at dawn into a taxi for the ride across Rio to their lodgings in the Olympic Village.
In his original account, Mr. Lochte said the car had been pulled over by armed men, one of whom put a gun against his head before taking the cash from his wallet. But police investigators said Thursday that Mr. Lochte and the others had acted more like small-minded vandals than the victims they claimed to be.
Making a stop around 6 a.m. Sunday at a Shell gas station, the men were obviously drunk, the stationâs owner said. They broke a soap dispenser in the bathroom, damaged a door, tore down a sign and urinated around the premises, the owner told reporters.
âOne of them was really worked up,â said Mr. Veloso, the police chief, who described Mr. Lochte, 32, as a kind of elder ringleader of the group.
Mr. Lochte had left Brazil before a judge ordered the police to seize his passport. Mr. Feigen, 26; Mr. Bentz, 20; and Mr. Conger, 21, remained in Brazil on Thursday evening.
The Brazilian police suggested on Thursday that Mr. Lochte and Mr. Feigen, the only swimmers who had given initial testimony to investigators about the episode, could face charges of providing false testimony about a crime.
Brazilian investigators said video evidence and witnesses showed that American swimmers had fabricated their account of being held up at gunpoint in Rio.
Mr. Bentz and Mr. Conger, who were pulled off their plane by the police on Wednesday in Rio, offered testimony on Thursday that contradicted Mr. Lochteâs accounts, police investigators said. The two men were still shouted down as âliarsâ by a crowd when they left a Rio police station.
The sight of the athletes wading through the crowd, along with a torrent of venomous comments by Brazilians on social media, raised concerns after a period in which Brazil and the United States had experienced a thawing of ties, with law enforcement officials working closely to identify potential security threats during the Olympics.
âThis episode will not in any way interfere in the relations between the U.S. and Brazil,â said Eliseu Padilha, the chief of staff for Brazilâs interim president, Michel Temer. Mr. Padilha added, âThis could have happened with individuals of any other nationality.â
Mr. Bentz and Mr. Conger flew back to the United States on Thursday night, the United States Olympic Committee said in a statement.
Using video footage, accounts from witnesses and testimony from the swimmers, investigators said a security guard had brandished a gun after one or more of the athletes vandalized the gas station bathroom.
In his original account, Mr. Lochte claimed that men claiming to be police officers had pulled over the taxi and that an assailant had put a cocked gun to his forehead before taking his money. He later altered that account, saying the taxi had stopped at a gas station so the athletes could use the bathroom.
Still, the description of the security guardâs use of a gun dovetailed with Mr. Lochteâs follow-up explanations of the episode, raising the possibility that the men had felt during the confusion of the moment that they were being pressured to hand over their money.
Video Shows Swimmersâ Return to Olympic Village
Mr. Veloso, the police chief, said he could not rule out that there was an extortion attempt by the guards, whom he described as âpublic agents,â a term that can be used for police officers or other members of the public security forces. Another police official clarified that the guards were off-duty prison guards working a second job at the gas station.
âFor the time being, nothing indicatesâ extortion, Mr. Veloso said, emphasizing that the guards were reacting to four large athletes âexhibiting, at a minimum, inadequate attitudes, breaking things and showing themselves ready to elevate the level of violence.â
In the midst of the confusion at the gas station, someone called the police, but by the time a police car arrived, the swimmers were gone. Witnesses, including a man who offered to translate for the swimmers, said they had offered to give money to the manager before leaving.
Mr. Lochteâs lawyer, Jeff Ostrow, said the video footage had corroborated the âprimary elementsâ of his clientâs descriptions of the episode.
âThere was a uniformed person with a gun who forced them to hand over their money,â Mr. Ostrow said.
Mr. Veloso said one of the first leads in the investigation had come from a taxi driver who gave a ride to two Brazilian women who had left the same party and discussed having romantic encounters with the swimmers.
âAt least one of the athletes may have had a motive for telling a story that wasnât true,â Mr. Veloso said, raising the possibility that the accounts were fabricated to disguise that the swimmers had remained at the party until almost sunrise. Mr. Veloso did not specify which of the swimmers might have had that motive.
Rio Official: Swimmers Made a Mistake
Still, Judge Marcello Rubioli, the head of the special court handling the case involving the swimmers, said that making a false claim in Brazil was ânot that seriousâ and âresults in very little punishment.â
âIf they are found guilty, they would just have to make a payment to an N.G.O. that does humanitarian work,â he continued, referring to a nongovernmental organization.
The new turns in the case raised tensions around Brazil, with some commentators questioning the role of American Olympic officials in providing confusing initial accounts and then shielding the swimmers from scrutiny. But Olympic officials in Rio seemed to be trying to play down the episode.
âNo apologies from him or from the other athletes are needed,â said Mario Andrada, a spokesman for the Rio Olympics organizing committee, referring to Mr. Lochte. âWe need to understand that these kids were trying to have fun.â
He added, âSometimes you take actions that you later regret.â
Some in Rio lamented the episode, though, emphasizing that they wished the police were always so efficient in clearing up reports of violent crime. Before the Olympics, the authorities had sought to ease fears by deploying a security force comprising 85,000 police officers and soldiers.
âThe real dilemma is that people in this city live in fear of crime,â said Eduardo Rangel, 64, the owner of store selling office supplies. âThe swimmers took advantage of the mess that exists around here to further denigrate the city. That doesnât mean Rio is some paradise without crime.â
Others in Rio, however, said they felt deeply insulted by the behavior of the American swimmers.
âThese guys from abroad think theyâre superior to us, that they can come here, make a mess, lie about it and stain the image of Brazil,â said Airton Rocha, 28, a waiter at a cafe. âWell, the law is the law, and it should apply to everyone in the same way.â
Late Thursday night, American Olympics officials issued an apology.
âThe behavior of these athletes is not acceptable, nor does it represent the values of Team USA or the conduct of the vast majority of its members,â said the statement, which was attributed to the organizationâs chief executive, Scott Blackmun.
âOn behalf of the United States Olympic Committee, we apologize to our hosts in Rio and the people of Brazil for this distracting ordeal in the midst of what should rightly be a celebration of excellence.â