Rio 2016’s organisers say they can “guarantee” the safety of everybody at the Olympics despite a series of alarming incidents, including an attack on a media bus on Tuesday evening.

Speaking on Wednesday, Rio 2016’s security director Luiz Fernando Correa told journalists that the bus, which was moving fast along a new highway, was hit by a rock, not a bullet.

“The forensic analysis was done here at the (main press centre) and the first findings confirm the bus was hit by a rock, which is worrying and intolerable,” said Correa.

“The final findings will be made available later today.

“We are talking about an urban area, densely populated. It would be impossible to have a perimeter to exclude a person in the range of throwing.

“We have no doubt the topography facilitated the attack. A younger person took the opportunity to throw a stone at a bus going through.

“We think this is an act of vandalism and not a criminal act with the intention of injuring one person so we need to increase the frequency of the mobile patrolling and police along the road.

“We are reinforcing the police presence.”

When pushed on Rio 2016’s overall security plan, the organising committee’s main spokesman Mario Andrada said: “Yes, we are convinced we can guarantee the safety of journalists, athletes and every guest here — that’s our primary responsibility and we can guarantee it.”

But despite airport-style security at the venues and 85,000 soldiers spread around the city, crime has become an unavoidable story at these Games.

That should probably not have come as a surprise to anybody — given the state of Brazil’s economy, political unrest and the glaring juxtaposition of poverty and wealth in Rio — but with the world’s attention focused on South America’s first Olympics, there are growing concerns at the number of incidents.

Athletes, diplomats and sports officials have been robbed, there have been a spate of thefts at the Olympic Village, security forces have performed at least two controlled explosions at sports venues and a local man was shot dead after the opening ceremony when he tried to mug a senior security official.

And Tuesday’s bus incident was not even the first involving journalists, as a stray bullet, fired from a favela at a police blimp, flew through the media workroom at the equestrian event on Saturday.

Lee Michaelson, an American reporter and former US Air Force captain, was on the media bus on Tuesday night and told Press Association Sport. “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.”

She also said the bus driver initially tried to stop but was told to keep moving by the dozen or so journalists on board, the first police vehicle to reach them did not appear to know what to do, there was no first-aid kit on the bus, medical assistance when they reached the press centre was minimal and police failed to interview them all.

Press Association photographer David Davies said of the incident: “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.”

Davies and Michaelson both said there were only minor injuries caused by the broken glass but Michaelson said her medical assistance amounted to some water to wash her cut and a tissue to dry it.

Correa was adamant that the impact was caused by a rock, or two rocks, but suggested it could have been fired by a catapult. He has promised a full forensic report later.

Andrada also said an investigation was under way to make sure the professional driver followed the correct protocol for such incidents and repeated his assurances that more patrols along the main transport routes would prevent this from happening again.

Spokesman Mark Adams said the International Olympic Committee was taking the incident “very seriously”.