RIO DE JANEIRO — Conflicting versions of an attack on a media bus dominated the International Olympic Committee’s Wednesday morning press briefing. The incident in question occurred roughly 15 hours earlier, when a bus traveling from the Deodoro venue cluster to the Media Transport Mall in the Olympic Park was hit by window-shattering projectiles. Of the 12 journalists on the bus, two suffered minor injuries because of the broken glass.

Rio Olympics head of security, Luiz Fernando Correa, repeatedly stated that rocks, not gunfire, hit the bus. He noted that forensic findings confirmed that.

When asked if he was 100 percent certain that rocks hit the bus, Correa said through a translator, “The information that says that it’s a stone is from public authorities who were there at the moment. That’s why I’m sure it was not gunfire.’’ Additionally, Correa considered the incident “an act of vandalism not a criminal act with the intent of injuring people.’’

But passengers on the bus said they heard gunshots and that the holes in the windows looked like they came from bullets. One passenger, Sherryl “Lee’’ Michaelson, a retired US Air Force captain working as a basketball reporter at the Games, attended the briefing, questioned Correa, and cast doubt on the projectiles being rocks, not bullets. Michaelson recalled the bus traveling at a high rate of speed when she heard two shots ring out.

“There were two points of impact, pop, pop,’’ said Michaelson. “I don’t want to accuse anybody of a cover-up. But I will not believe this was stone-throwing unless I see a forensic and a ballistics report, looking . . . at the glass, which was the point of impact in not one but two places, from a competent, forensic authority that has no reason to put any good spin on it.’’

In her mind, she added: “It was clearly bullets.’’

The attack on the media bus was the latest incident to raise concerns about security at the Rio Olympics. The official version of events differed greatly from the passengers’ recollection, prompting suspicions that authorities were concealing the truth, or, at least, downplaying critical security lapses at the Games.

Prior to the Games, the spokesman for the Rio Organizing committee, Mario Andrada, said Rio de Janeiro would be “the safest city in the world’’ during the event. On Wednesday, Andrada was asked if he regretted that statement.

“I don’t regret saying that,’’ said Andrada. “That’s because that’s our mission. It’s to make Rio the safest city in the world.’’

“When an athlete goes to competition, he says I’m going to win. If he doesn’t win, he doesn’t regret saying that. Because that is something that provides the team that is working with him the necessary energy for not dropping the ball. If we drop the ball in security, we need to get our act together and we need to keep our eye on the mission that we have, which is to make Rio the safest city in the world during the Games.’’

A stray bullet from a favela hit the media tent near the equestrian center on Saturday. Rio Olympics officials believe the shooter was aiming for security cameras on a blimp hovering over the venue. Roughly two hours before the men’s cycling road race ended on Saturday, Brazil’s anti-bomb squad destroyed a suspicious package near the finish with a controlled explosion. And that was only the first full day of competition.

Last Thursday, a few miles from the Olympic Park and Athletes Village, an armed motorcyclist attempted to mug a man in his car. The man pulled the attacker into the car, they struggled, and the attacker was killed with his own gun. At an Ipanema coffee shop, a photographer had $40,000 worth of gear stolen along with his official, numbered photo vest. The photographer later spotted someone wearing his photo vest and getting through security at the archery venue, even though the person did not have the proper press credential.

Also, journalists have reported media bus drivers getting lost going to or returning from venues, and sometimes taking accidental detours close to or through favelas.

When asked for his evaluation of Rio’s security efforts to date, Correa said, “Generally, we do have incidents. Our utopian quest is a city without incidents, but in a big city like Rio, we have incidents.’’

Then, Correa spoke proudly about declines in Rio’s crime rates and urban violence during the Games and said, “We believe this is due to a lot of patrolling.’’ To better protect the bus route between Deodoro and the Media Transport Mall, Correa said the police presence on the road would be reinforced.

In an attempt to make the Games safe, approximately 85,000 soldiers and police officers have been deployed throughout the city, twice as many as London had during the 2012 Summer Games.

In the neighborhood of Barra da Tijuca, home to the Olympic Park and Athletes Village, security personnel blanket the major streets and surround the venues. They seem to be everywhere, large guns slung over their shoulders.

But given what happened with the media bus and other incidents, the question remains: Are security forces being smartly deployed throughout Rio?

“In a city as big as Rio, there is going to be crime whether there is an Olympics or not,’’ said Juliette Kayyem, founder of security consulting firm Kayyem Solutions and former assistant secretary at the Department of Homeland Security. “The question for the Rio committee is whether they’ve adequately deployed resources and personnel that minimizes risk to the Olympic community. While each individual incident may not seem like a big deal by itself, at some stage the cumulative numbers tell you something.’’

Shira Springer can be reached at springer@globe.com. Follow her on Twitter @ShiraSpringer