Rio de Janeiro: Brazilian military carried out a controlled explosion near the Copacabana finish line of Rio Olympics men's road cycling race on Saturday, officials said.
Military bomb disposal experts were at the scene of the explosion and kept crowds away with police.
Simone Barreto, a media manager at the Fort Copacabana site used for the cycling, told AFP that the explosion was staged as a precaution.
"Forces responsible for security found an object, sort of a bag, outside the venue and outside the security perimeter.
"They decided to implement the procedure and to implode the object. The situation is now normal."
The explosion stunned crowds gathering for the end of the race. The race leaders were about 100 kilometers (60 miles) away at the time.
In further violence on Friday, police gunned down a mugger outside the ceremony venue, the Maracana stadium, and a woman was shot and killed by armed assailants near the Olympic Boulevard.
The events overshadowed a busy opening day of action in which little-known American teenager Virginia Thrasher became the first gold-medallist, in the women's 10m air rifle, the first of 306 medal events.
In swimming, China's Sun Yang will defend his 400m crown later on Saturday, and Britain's Tour de France Chris Froome was among the road race competitors.
Serbian rowers Milos Vasic and Nenad Bedik capsized in choppy waters at the Rodrigo de Freitas lagoon, while Iran's Ghader Mizbani suffered a terrifying crash in the cycling race.