Charleston fire officials are trying to determine the cause of an early morning blaze that damaged an insurance building on James Island today.

A police officer reported the fire after spotting smoke coming from the Allstate building at 571 Folly Road at 1:13 a.m., Charleston Fire Department public information officer Mark Ruppel said.

Firefighters saw heavy smoke coming from the building when they arrived. They quickly moved to contain the fire, Ruppel said.

The blaze appeared to originate in a stairwell, but that has not been confirmed, Ruppel said. The building was unoccupied at the time and no one was injured.

Ruppel described damage to the building as moderate.