Massive 5-alarm fire erupts at structure near March Air Reserve Base in Riverside County

RIVERSIDE COUNTY (KABC) -- A massive 5-alarm fire erupted Monday at a commercial warehouse near March Air Reserve Base in Riverside County, igniting bundles of cardboard and other materials outside the structure and quickly spreading to at least 10 acres, officials said.

The blaze was reported shortly after 1:30 p.m. in the 22000 block of Opportunity Way, according to the Riverside County Fire Department.

The fire sent an enormous column of thick black smoke into the air as firefighters on the ground and atop aerial ladders used hoses to douse the flames.

There were no immediate reports of injuries.

The cause of the fire is unknown.

DEVELOPING: More details will be added to this report as they become available.