Police have opened an arson investigation into a Waipahu warehouse fire.

A warehouse belonging to West Oahu Roofing Inc. was fully involved when firefighters arrived Sunday at 12:58 p.m.

The business was closed and no one was inside the two-story warehouse at 94-170 Leoole St. at the time of the fire, the fire department said.

No injuries were reported. Damage was estimated at more than $20,000. The cause of the fire was unknown at the time.

Eleven fire companies responded to the blaze, and the fire was under control by 1:30 p.m. and extinguished at 2:42 p.m.