Assistant State Fire Marshal Michael G. Chionchio said the automatic sprinkler system extinguished the blaze Tuesday night in Middletown.

The Delaware Office of the State Fire Marshal has determined that last night’s building fire at the Amazon fulfillment center in Middletown was accidental.

Volunteer Hose Company of Middletown responded to a report of a fire at about 9:30 p.m., inside the processing area at the building at 560 Merrimac Avenue.

When firefighters arrived, the sprinkler system had already extinguished the fire.

State fire investigators were called to the scene to conduct the investigation.

The fire occurred at the mezzanine level of the building when static electricity ignited leaking vapor from a container of assorted aerosol cans, said Assistant State Fire Marshal Michael G. Chionchio.

The area where the fire began was protected by a fully automatic fire sprinkler system which put the fire out and prevented the fire from spreading.

Fire damage was contained to the stockpile of products and estimated at $1,000, Chionchio said.

There were no reported injuries.