A small fire that produced a lot of smoke inside downtown Salt Lake City's Walker Center Building was determined to be accidental in origin.

The fire, which involved several floors of the 16-story building, 175 S. Main, was confined to a utility pipe chase but caused about $100,000 in damage, according to Salt Lake City Deputy Fire Chief Dan Andrus.

Fire crews investigated the problem at the 100-year-old building for three hours Thursday starting about 7 p.m., blocking off several downtown streets. The exact cause of the fire had not been determined Friday afternoon. All possible causes were being looked at, according to Andrus, including whether an electrical conduit was to blame.