RIO DE JANEIRO (AFP) - Rio Olympics organisers said they were investigating on Tuesday after a large, suspended TV camera plunged 20m onto a concourse at Olympic Park.

Seven people were injured, none seriously, after the incident when ropes snapped and a "spidercam" the size of a small motorbike plummeted to earth on Monday.

Footage showed two shocked-looking women with blood around their nose and arm respectively and a girl on a stretcher being loaded into an ambulance.

"Thankfully no one was seriously injured. We're trying to work out with security and the people responsible what exactly happened," said International Olympic Committee spokesman Mark Adams.

The camera was being used by the official Olympic Broadcasting Services, which realised the camera was at risk of falling and isolated the area below.

"They thought the wire could hold for a little bit more. (But) the camera fell and hit one of the fences that was isolating the area," a Games spokesperson told AFP.

It was not the first infrastructure problem at the Games, where the marathon swimming starting platform was washed onto Copacabana beach by strong currents.

Safety concerns have also been prominent after two stray bullets hit the equestrian venue and stone-throwing youths attacked a media bus.