RIO DE JANEIRO — Forty-eight hours after Olympic officials issued an apology to four American swimmers who said they were robbed at gunpoint, Brazilian authorities continued to investigate their claims and sought to prevent them from leaving the country so they could further question them.

Two of the swimmers, Gunnar Bentz and Jack Conger, were pulled off their return flight to the United States by Brazilian authorities late Wednesday at Rio airport, according to the United States Olympic Committee.

Police showed up at the Olympic village on Wednesday to confiscate the passports of Ryan Lochte and Jimmy Feigen but found neither swimmer there. Lochte had already returned to the U.S., according to the police.

“The swim team moved out of the village after the competition ended,” said Patrick Sandusky, a U.S. Olympic Committee spokesman, who added that “as part of our standard security protocol, we do not make athlete travel plans public.”

Feigen was reportedly still in Brazil, telling his hometown newspaper, the San Antonio News-Express, “I can’t talk right now.”

With all its uncertainties and contradictions, the incident has captivated residents of this city, prompting speculation about what happened in the early morning hours on Sunday.

Local television has replayed security video — obtained by a British newspaper — of the swimmers returning to the village shortly before 7 a.m. that morning.

Police said they are now scrutinizing additional video from a gas station where the crime allegedly took place.

“I can’t comment on contradictions in any stories, and I can’t refute any statements that were given,” said Officer Alexandre Braga of the special police station for tourism support. “This case is delicate and receiving a lot of attention; we must be very careful.”

The news broke Sunday when Lochte’s mother told a reporter that her son had called her about the robbery.

U.S. Olympic Committee officials quickly contacted Lochte, who denied that a crime had taken place. The International Olympic Committee announced that news reports of a robbery were “absolutely not true.”

But Lochte, who won gold in the 800-meter freestyle relay last week, subsequently changed his story.

The 12-time medalist said that, after the swimming portion of the 2016 Summer Games ended on Saturday night, he and his teammates went to the France House to celebrate.

There had been some question about when they left; police now believe the four departed at 5:45 a.m.

Lochte said they were returning to the village when their taxi was stopped by armed men flashing what appeared to be police badges.

“They pulled out their guns, they told the other swimmers to get down on the ground — they got down on the ground,” Lochte told NBC News. “I refused, I was like, we didn’t do anything wrong, so — I’m not getting down on the ground.

“And then the guy pulled out his gun, he cocked it, put it to my forehead and he said, ‘Get down,’ and I put my hands up, I was like, ‘whatever.’ “

The USOC was initially cautious, beginning its news release with the words: “According to four members of the U.S. Olympic Swimming team … .”

Police, who subsequently interviewed the swimmers, have yet to locate the taxi driver. In the meantime, the Rio 2016 organizing committee issued its apology on Monday.

“We have requested the security authorities … need to make sure everybody is safe everywhere in the city,” spokesman Mario Andrada said. “We apologize to those involved and regret that violence is an issue in these Games.”

The alleged robbery was merely the latest negative publicity for an Olympics that has suffered through one security concern after another.

Two Australian rowing coaches were robbed in Ipanema, and an Olympic security officer was shot to death after taking a wrong turn into a favela. The Games’ chief of security was attacked by knife-wielding men as he left Maracana Stadium after the opening ceremony.

Stray bullets have landed in the equestrian venue in Deodoro on two occasions, and a bus carrying journalists in the area had its windows shattered. Rio officials insisted that thrown rocks were to blame.

None of this squared with Mayor Eduardo Paes’ proclamation before the Games that his city would be “the safest place in the world.”

Lowell Gustafson, a Villanova University professor who has studied Latin American politics, said authorities have a history of downplaying bad news.

“What seems fairly traditional is for the Brazilian police and bureaucracy to call into question anyone making accusations,” Gustafson said. “They want to say that this doesn’t happen in Brazil.”

But reported contradictions in the swimmers’ story, and unusual details such as the fact that robbers did not take the athletes’ cellphones and conflicting statements about the number of assailants, have continued to puzzle investigators.

“We’re currently trying to get all the information that is available,” Braga said.