A man in a funeral procession holds a sign that reads, The sadness of mothers of children killed, doesn't have a price. (AP)

RIO DE JANEIRO — On a recent morning on the shore of Guanabara Bay, 37-year-old Jose Carlos Daniel stood with his fishing pole and discussed his night job as a doorman.

"I'm concerned about violence," he said through a translator. "I've seen robberies, fights. I'm not very optimistic about security during the [Olympic] Games."

In the run-up to the Summer Olympic Games, which officially begin Aug. 5, much international attention has been paid to the Zika virus' presence in Brazil, the political unrest in the wake of the impeachment of President Dilma Rousseff and the omnipresent fear of terrorism.

But the growing concern, security experts told Yahoo Sports, is local crime.

View photos A black banner hangs in a Rio favela to mourn the death of teenager Eduardo Felipe Santos Victor. (AP) More

Rio has been roiled about news of a gang rape of a 16-year-old girl in a slum not far from the Olympic venues. Several men reportedly attacked the teenager and filmed the assault. In May, a 17-year-old woman was on her way to the Rio airport to pick up a relative when a gang approached on a roadway and shot her through her car window. And there has already been a crime on Olympians, as two Spanish sailors were robbed at gunpoint in Santa Teresa, a picturesque hillside area of Rio that attracts tourists but has some very dangerous spots.

Every year, an estimated 40,000 Brazilians die from gun-related incidents. The number of murders in Rio is up 15.4 percent from last year, according to one recent study, and street robberies have risen by nearly 25 percent.

It's unlikely that many Olympians will venture into troubled areas during the Games, but the proximity of those pockets to the tourist sectors will cause worry throughout the month of August.

"The unique challenge of Rio is the well-armed and aggressive criminal groups," said Antonio Sampaio, a security expert with the International Institute for Strategic Studies. "It remains something we haven't seen.

"I don't think the groups will deliberately target public places; this risk I'm talking about is more taking the form of gunfights," he continued, stressing his belief that the threat to visitors is low. "It's a hilly terrain and the slums are in hills. Sometimes you can actually see the gunfights. You can get an emerging battle in an urban city. If there is a gunfight during the Olympics, that is the most likely form of risk."

Fears of terrorism in Brazil, however, are more muted.

The U.S. State Department has issued a terrorism warning to travellers to Europe for the Euro 2016 soccer tournament and other summer events on that continent, but one official doesn't expect a similar alert for Rio-bound Americans.

"We don't have any information or recent incidents to lead us to believe there's a specific risk for Brazil," said Michelle Bernier-Toth, who is the State Department's managing director for overseas citizens services.

That's somewhat reassuring, and it comes from months of planning.

"The Department of State works very closely with the host government," Bernier-Toth told Yahoo Sports. "We have been doing this for over a year in Brazil to assess the situation for both our teams and private citizens. We know exactly what is happening, and what the response would be. So we can be prepared for the expected and unexpected."

Case in point: a federal judge recently ordered an ankle bracelet for a restaurant owner in the south of Brazil who had been "preparing vigorously … for the Muslim holy war," according to the results of an investigation. The bracelet is to stay on for the duration of the Olympics, and points to the depth of preparation for the Rio Games: this federal investigation has been going on for three years.

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