Over 100 spectators were injured after a grandstand in Brazil collapsed in on itself during a car race in the city of Quatro Pontes.

Of the injuries, 22 were deemed critical after the 500-capacity seating area fell down like a string of dominoes battered by the wind. Other racing fans looked on, aghast.

As you can see from the video footage below, the seating tumbles down very suddenly, prompting an immediate official investigation by the state of Paraná in southern Brazil. Structural issues have initially been reported as the cause of the accident, though a more in-depth review will reveal more.

Here's hoping there's nothing like this when the Brazilians host the next World Cup in 2016.

Check out the astonishing footage below.