Military police in Rio de Janeiro are stepping up security after projectiles struck a bus carrying journalists to the main Olympic Park, the organizing committee for the games said.
While authorities said it was not immediately clear what struck the bus, a retired U.S. Air Force captain who now writes about women's basketball said she was certain it was gunfire.
Britain's Press Association on Wednesday quoted Lee Michaelson, who was on the bus Tuesday, as saying that she instinctively hit the floor when she heard the sound of gunfire and "hollered to the others ... 'Get down! Get down! We are taking fire.'"
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"I know what a gun sounds like," she said. "It was the sound before I ever saw the glass (shatter) or anything."
The Rio organizing committee said the driver heard a noise from inside the bus, which he thought was photography equipment falling down.
When he checked his rear view mirror, he found the journalists were lying on the ground. He saw a police car and stopped.
"At this time, he realized that two windows on the same side of the bus were broken," the committee said in a statement. "He resumed the route under the escort of the police car and the broken windows began to give way further."
Michaelson says both the bus driver and Olympic officials made mistakes. The driver slowed down and pulled over, which she says is "precisely the opposite of what he should have done, which was to put the gas on and floor it."
When they returned to the Olympic park, she says there was no medical help waiting, despite some passengers being injured and bleeding.
A dozen journalists on the bus suffered minor injuries.
"There was kind of a popping noise and something hit two windows on the side of the bus and left two hole marks, which looked like bullet holes," David Davies, a photographer for the British-based news agency Press Association, told the AP.
The bus was traveling from the northern venue cluster of Deodoro to the main Olympic Park in the suburb of Barra da Tijuca.
The incident raises more concerns about security at the games.
Rio is deploying about 85,000 soldiers and police to secure the games, twice as many as London did four years ago.
On Saturday, a stray bullet flew through the roof of a media tent at the Olympic Equestrian Center. Officials said it had been fired from a hillside favela, but said the games had not been targeted. Organizers said the intended target was probably a security camera on a blimp.