A massive fire broke out around 7 a.m. Tuesday that is sending thick black smoke over San Francisco, and distracting drivers during their commute on Highway 101.

The five-alarm fire has engulfed multiple buildings near the intersection of 14th Street between Folsom and South Van Ness, across from Rainbow Grocery, at the border between SoMa and the Mission District. Video posted to Twitter shows a large and out-of-control blaze, and the San Francisco Fire Department spraying water over it from the tops of craned ladders.

One southbound lane of 101 was blocked off, as the Chronicle reported, and KPIX reports that the Division Street onramp to 101 was closed as well.

Photo: Andrew Warren

It's still unclear which and how many buildings are involved in the fire.

KPIX initially reported that the fire was in a "multi-story building on the 100 block of 13th Street." Firefighters posted an initial report that the fire was burning at 14th and Shotwell.

Update: One of the buildings involved in the blaze, and perhaps a source of major fuel, was Bartfeld Sales Co. at 140 14th Street, a 73-year-old family-owned construction supply business that was full of lumber. KTVU spoke with one of the owners, who said the building was on fire when his father arrived at work this morning.

Update 10 a.m.: Fire crews say the fire was under control as of 10 a.m.

And BrokeAss Stuart is reporting that as many as six buildings may have been damaged or destroyed in the blaze.

This post has been updated throughout.