A fire was threatening the course that will stage the Olympic mountain bike competition on Monday after a controlled rubbish burn spread out of control in high winds.
Photographs posted on the Twitter page of a Canadian Cyclist website showed flames licking the hills surrounding the venue at Deodoro, 43km (27 miles) from the main Olympic Park.
Cycling governing body the UCI said it was monitoring the situation.
"We are aware that there was a fire this afternoon in the vicinity of the Rio 2016 Mountain Bike course," it said.
"It is understood the fire is now under control. Assessment of any potential impact on the Mountain Bike course will be made tomorrow."
Rio 2016 organisers issued a statement later, saying the fire had started in a forest behind the nearby shooting venue and that nobody was injured.
"High winds made the fire advance close to the mountain bike venue. During the firefighters work to contain it, the fire changed it's direction and doesn't represent any risk to the venue."
Firefighters were trying to stop the flames spreading to a local community, organisers said.
Image: The official logo for the Rio 2016 Olympics games
Photograph: Buda Mendes/Getty Images