Alan Gomez

USA TODAY

RIO DE JANEIRO — Despite a slew of robberies and terrorism arrests in the weeks leading up to Friday's opening ceremony, U.S. officials say they are confident that Brazilian security forces can fully protect the Olympic Games.

American law enforcement has spent years training Brazilian officials and increased the level of information they share with their Brazilian counterparts. But the U.S. security footprint in Rio will be small throughout the three weeks of events, leaving the brunt of security work up to the Brazilians.

Armour: Problems and promise — 6 story lines for the Rio Olympics

Brazil has pooled its local, state and federal law enforcement to deploy 85,000 people to secure the Games, more than double the number used in London in 2012. On Friday, Brazil's O Globo newspaper reported that Brazil has increased that figure to 100,000 as news of violence has swept through Rio.

In recent weeks, the cases have added up.

A New Zealand-born jiu jitsu fighter living in Brazil said he was kidnapped by corrupt police officers demanding money. A man vomited on a Chinese hurdler as part of a hoax to rob the Olympian and a cameraman. The Australian team was robbed of a laptop and Zika-protective team shirts during a fire evacuation at their Olympic housing. On Thursday night, a man whom police described as a Russian diplomat was involved in a scuffle with an alleged robber in the city when a gun went off, killing the assailant; Russian officials have denied the man was part of their diplomatic service. And a sleeping firefighter was allegedly raped inside the Olympic Park near the velodrome, an indoor cycling arena, according to the Brazilian newspaper O Globo.

"Every Olympic environment involves challenges, but from what we have seen thus far, the Rio Organizing Committee and the people of Brazil are ready to host a great Games," USOC spokesman Patrick Sandusky said via email. "We can't wait to get started."

Olympic boxer arrested on sexual assault allegations

Brazilian authorities also arrested 10 people who expressed loyalty to the Islamic State who were believed to be planning terrorist attacks in Rio during the Games. And there has been an increase in traffic on social media sites used by ISIL and other terrorist networks, much of which has been translated into Portuguese and included suggested targets for lone-wolf attackers, according to the U.S.-based SITE Intelligence Group.

Those threats have been compounded by shootouts and armed robberies throughout the city, which has surprised many Brazilians, including Mauricio Santoro, a political science professor at Rio de Janeiro State University.

Santoro said he expected crime to go down as the Olympics approached because of the heavy security presence throughout Rio. Instead, he said criminal gangs have closely monitored how federal, state and local security officials have deployed their units.

"They've identified the gaps in the security strategy," Santoro said.

U.S. officials say they're trying to counter all those threats by training and working closely with Brazilian officials and other law enforcement agencies around the world. Many will be working out of a newly created International Police Coordination Center that brings together government officials from different countries.

2016 Rio Olympics: How to watch the Opening Ceremony

Brazil's security forces have long been mired with corruption and ties to organized crime throughout the country. But Steve Moore, the FBI's legal attache in Brazil, said they have been working with carefully selected, U.S.-trained Brazilians for several years now, reducing the risk that sensitive information will fall into the wrong hands.

“The key to this is that we work closely with the Brazilian federal police and share information with their specialized units," Moore said.

While much of that has gone on behind the scenes, American tourists in Rio say they feel safe — for now.

Peter and Donna Tomozawa, a retired couple from Los Angeles, walked along Rio's famed Copacabana Beach on Thursday night taking in the dizzying sights and sounds around them. They said this was the first of their three Olympic Games that made them think hard about security concerns, but they decided to take the plunge anyway.

"It's always on your mind, but you gotta live," said Peter Tomozawa. "You can't let the bad guys stop you from doing good things."

"But just in case, we have nothing on us," interjected Donna Tomozawa. "You could rob us and we don't have anything on us."