A vacant SoMa building was the site of a two-alarm fire Monday morning, after a blaze broke out in the structure's attic.

According to a spokesperson with the San Francisco Fire Department, the fire began at around 4:45 a.m. in the attic of what was once known as the Dempster Printing Building, a four-story structure at 447 Minna Street, between Fifth and Sixth Streets.

The building, which KRON 4 reports was constructed in 1907, is "part of the 5M development project, one of the largest and most anticipated mixed-use developments San Francisco has seen in the past few years," reports the SF Chronicle. (The Chron's parent company, the Hearst Corporation, is the developer of this "most anticipated" project, it should be noted. You can learn more about the development and its level of anticipation here.)

By 6:30, the SFFD had controlled the blaze, and ABC 7 reports that firefighters smashed the windows of the unoccupied structure "to ventilate the building so the fire doesn't start up again."

As of publication time, the cause of the fire is unknown. "When asked if they think squatters were inside and were responsible for starting the blaze, they said it's too early to tell," reports ABC 7, saying that "There was construction equipment on the lower floors, so there were possible renovations underway." In opposition, an SFPD spokesperson who spoke to the Chron says that "it appeared no one was recently inside the empty, 12,000-square-foot building."