Fireworks blamed for $3-million warehouse fire

Witnesses: Group of young men shooting fireworks at mattresses

A major fire is under investigation.

Investigators suspect illegal fireworks sparked a fire that injured four firefighters and caused up to $3 million in damage to three warehouses in South Los Angeles.

Officials say witnesses reported seeing a group of young men shooting fireworks at mattresses outside one of the warehouses Saturday night.

The blaze spread to two other warehouses.