The Rio 2016 organising committee has confirmed a suspicious package was detonated at the Olympic cycle road race venue here on Saturday.
The spokesman said: "The security services found a suspicious package close the cycle road race finish line in Copacabana and as a precaution decided to perform a controlled explosion. There is no impact to the race which is ongoing."
Fans watching the race were startled when they heard a loud noise close to the waterfront.
A bomb disposal unit was seen near the finish line, as were half a dozen military police officers. The area has been cordoned off.
One cycling fan told: ‘I thought it was a gun shot at first. Everyone stood up and looked a bit concerned but then sat back down so I presumed it was a firework.’
There have not been any reports of injuries and the race has not been stopped or diverted.
An official said the item was a small bag and that the police bomb squad's action was a precaution, reports Xinhua.