Security at the Olympics is to be stepped up after bullets were believed to have been fired at a media bus.
Two windows were smashed as the bus travelled between the Deodoro zone and the main transport mall in Rio's Olympic Park at around 7.30pm local time (11.30pm Irish Time), with about a dozen media on board.
A Press Association photographer, travelling on the bus at the time of the incident, said: "We were travelling from the hockey venue to the main press centre. I was sitting at the back. There was a popping, cracking noise.
"The bus didn't come to a stop but paused. Everyone was on the floor so I got on the floor as well.
"The bus driver stopped the bus about half a minute afterwards. People started shouting 'just keep going'. After a couple of minutes we had a police escort.
"A few minutes later the bus pulled over on the motorway and the driver spoke to the police. Then we all got back on the bus and came back to the main transport mall.
"There were minor injuries from glass shards but nobody was seriously hurt."
Mario Andrada, the chief spokesman for Rio 2016's organising committee, said: "We don't know yet if the bus was shot, or it was a stone."
But Lee Michaelson, a reporter on women's basketball who is also a retired US Air Force captain, was in no doubt.
She told the Press Association: "I know what a gun sounds like. There was a very distinctive sound of the report of a gun. It was the sound before I ever saw the glass or anything.
"With my background and training, I got down on the floor as much as I could and I hollered to the others to get down.
"The others were just beginning to respond. I started yelling at them, 'Get down, get down, we are taking fire'."
The International Olympic Committee said security forces are investigating the incident.
An IOC statement read: "We are aware that a media bus travelling from Deodoro to Barra on the Transcarioca had two windows broken by objects coming from the surrounding area.
"The security authorities are now investigating the incident and we await their report before making further comment."
The photographer continued: "There were pierced holes in the glass when it happened.
"The two windows did not shatter immediately but one of them shattered as we drove along the motorway.
"That is when the driver pulled over and talked to a policeman."
A statement from the Rio Olympic Games organising committee (ROCOG) read: "According to the driver's report, the media transport bus left the Youth Arena in Deodoro at around 1930 this evening, Tuesday August 9, travelling towards the Olympic Park.
"When on the expressway Transolimpica, near Curicica, the driver heard a noise from inside the bus which he thought was photography equipment falling down.
"Immediately, he looked in the rear-view mirror and noticed that the passengers were lying on the ground.
"He continued to drive for a few metres until he saw a police car and stopped. At this time, he realised that two windows on the same side of the bus were broken.
"The driver will provide a statement to police this evening accompanied by a security manager of the Organising Committee of the Rio 2016 Olympic Games.
"Also tonight the bus will be subjected to an official inspection by the police. Preliminary results will be released as they become available.
"The area defense general co-ordinator (CGDA) of the army and the military police informed that patrols are being increased in the area."
The incident on Tuesday is the latest of several to blight the Games.
On Saturday a bullet flew through the side of the media work room at Deodoro.
It was confirmed on Monday by Andrada that the bullet was fired at a security camera on a police blimp from one of the Brazilian city's favelas and the international equestrian media were not the intended target.
"According to the security forces, the bullet came from a community far from here," Andrada said.
"They were aiming at the blimp which carries cameras.
"The same source, from the ministry of defence, says the first findings showed that the bullet arrived with low energy and low speed."
Addressing the bus attack, Andrada said three of the 12 journalists on the bus suffered minor injuries.