The blaze at a warehouse building in the 2100 block of Emmorton Park Road, which started at 1:16 p.m., was caused by an electric heater placed too close to combustibles, according to a notice of investigation from the Maryland State Fire Marshal's office.
No one was injured in the fire. Twenty firefighters spent 30 minutes trying to control it, according to the notice.
"The incident was originally received as a automatic alarm with sprinkler activation," the notice said. "Fire suppression crews arrived and observed smoke conditions coming from the building. Further investigation by fire suppression crews located a fire inside of the warehouse being controlled by the building's sprinkler system."
Firefighters from Joppa-Magnolia, Abingdon, Aberdeen Proving Ground and Bel Air fire stations, as well as the Harford County hazmat team, responded to the fire.
The incident brings the total amount of property damaged in fires this weekend to about $390,000.
Harford firefighters stayed busy Saturday fighting fires in Aberdeen, Joppa and Forest Hill.