RIO DE JANEIRO – At least six people died, 32 people were injured and about 20 are missing after several giant rocks collapsed from a geological canyon and fell onto four boats on Furnas Lake in Brazil’s southeast Minas Gerais state, rescue teams said Saturday.

The incident occurred Saturday afternoon when, for unknown reasons, large rocks fell from the canyon that surrounds Furnas Lake, near Capitolio City, about 300 km from Belo Horizonte, state capital of Minas Gerais.

The rocks hit four boats that were on sightseeing tours at the time.

Heavy rains were recorded Saturday morning in the region, leading some geologists to believe that a waterspout in the canyon may have caused the rocks to fall.