Updated

More than 100 people have been injured -- 22 critically -- after a grandstand collapsed during a car race in Brazil.

Video footage shows the metal stand crumpling in less than a second at the race in the southern state of Parana.

Authorities have launched an official investigation into the accident but said structural faults may have caused the collapse.

Officials said at least 111 people were injured as the stand gave way at the race in Quatro Pontes.

Brazil's TV Taroba showed the footage and the chaos that followed, with the injured being treated at the scene.

It is thought at least 500 people were sitting on the stands when the accident happened.

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