An explosion Friday at a metal factory in the countryside of Brazil's most populous state killed four people and seriously injured at least 30 others, officials said.

Dozens of firefighters and rescue teams were sent to the site of the explosion in the city of Cabreuva, São Paulo Gov. Tarcisio de Freitas said on social media. Cabreuva lies about 60 miles northwest of the city of São Paulo.

JOHANNESBURG BUILDING FIRE LEAVES AT LEAST 73 DEAD, 52 INJURED

Footage on Brazilian TV broadcasters showed the factory completely destroyed by the explosion.

Local media outlets said the blast was triggered by overheating equipment, and that hospitals in the area had been warned there would be a big influx of injured patients.