Updated

SIMI VALLEY, Calif. -- California fire authorities say one person has been found dead after an explosion at a business in a Simi Valley industrial area.

Ventura County fire spokesman Ron Oatman says three other people were injured in the explosion shortly after 1 p.m.

Oatman says the building at least partially collapsed and firefighters backed out after discovering the fatality.

Businesses in a half-mile radius have been evacuated while authorities determine what they are dealing with. The blast also blew a hole in the building's roof.

Simi Valley is west of Los Angeles.