People have been seeing smoke rising off Angel Island on  and they're tweeting about it, but it's all okay and it's not a wildfire. They're just burning piles of brush and dead trees to avoid the chance of wildfires later.

California State Parks is conducting prescribed pile burning with the help of Marin County Fire today in Angel Island State Park, and it's ongoing until 7 p.m. Wednesday. The fire agency tweeted on Tuesday that this controlled burn would be starting today, and would likely go on for "2 to 3 days."

"Do not call 9-1-1," they add.

Mostly, people seem to be assuming it's a prescribed burn, and they're asking Twitter and local news stations to confirm.

And NBC Bay Area sent their chopper out there to get a closer look.