An automatic sprinkler system did its job during an early morning fire Tuesday at Yorktown Cinema in Lombard, officials said.

Firefighters responded to an automatic alarm at 4:15 a.m. at the movie theater and found heavy smoke coming from a storage room where cleaning supplies were stored. The sprinkler system had put out a small fire. Officials estimated damage from smoke and water to be about $30,000.

After investigating the fire, Lombard Battalion Chief Mike Torrence said the fire had been ruled accidental. A cleaning person had been in the storage room about 30 minutes before the fire started and used a lighter to burn a piece of mop head off and then put the mop head back on a storage shelf and left the room, Torrence said.

The investigation has been closed.