LAS VEGAS - A smoky two-alarm fire in a Las Vegas Strip casino storage facility was considered accidental, but a fire official said Friday the exact cause remained under investigation.

Most of the damage from the Thursday night fire was from water that poured from fire sprinklers that helped contain flames at the MGM Mirage office and warehouse structure, Clark County fire spokesman Scott Allison said.

A second alarm brought additional firefighters shortly after the 8:30 a.m. alarm at the MGM Mirage Events Center off Industrial Road near The Mirage hotel-casino. Allison said no one was at work when the fire was reported.

Investigators found small ignition devices in a corner of the warehouse where production equipment is stored for casino stage shows, Allison said. However, he said they were unable to immediately determine whether the igniters sparked the fire.

No injuries were reported and no damage estimate was immediately available, Allison said.