A fire broke out on a roof deck early this morning at 764 Union St. near Mason. No one was hurt, but it caused an estimated $120,000 in damage, according to San Francisco Fire Department spokesperson Mindy Talmadge.

The fire broke out around 3:13am and was contained by 3:38am. A two-alarm fire was called because of the potential for the fire to jump to another building, Talmadge said, but it wasn't needed. A propane tank on the deck also caught fire. SFFD called for investigators to determine the cause.

Most of the damage was to the top floor of the building, Talmadge said, at 762 and 764 Union St. The damage is estimated at $100,000 to the building and $20,000 to the contents. The rear unit, 760 Union St., had no damage.