Firefighters are battling a vegetation fire burning near Shockey Truck Trail and the Campo Indian Reservation in the East County, Cal Fire officials confirmed Sunday.
Cal Fire officials said the "Shockey Fire" sparked around 12:15 p.m.
By 2:15 p.m., the blaze had burned more than 300 acres. Officials said structures were threatened.
By 2:30 p.m., authorities began issuing mandatory evacuations in the area.
A reverse 911 call went out to at least 77 homes between the 500 and 2100 blocks of Tierra Del Sol Road, Lt. Scott Amos told NBC 7.
Crews are requesting evacuations of everything to the left line of the fire.
The Red Cross has set up an evacuation center at Golden Acorn Casino on Golden Acorn Way.
According to officials, 15 engines, four crews, four air tankers and two helicopters are at the scene.
Lt. Amos said the blaze is burning southeast at a quick rate of spread.
A map of the area shows it's near Campo Road and Church Road.
No injuries have been reported.
Check back for updates on this developing story.