Multiple San Francisco fire department crews are currently at work battling a 2-alarm fire on the third floor of a home in Presidio Heights.

STRUCTURE FIRE (update): 2nd Alarm called by crews having difficulty with fire on 300 block of Walnut.

— Emergency_In_SF (@Emergency_In_SF) February 4, 2014

SFFD Spokeswomen Mindy Talmadge said there are two buildings involved and crews were working to ventilate the roof.

CBS5's aerial footage, which was covering a manhunt in Potrero Hill just prior, caught a couple shots of the fire:

We'll update as we know more.