As the Chronicle and CBS SF report, a 300-acre wildfire in the Contra Loma Regional Park area of Antioch Wednesday, a blaze which began sometime this afternoon around 4 p.m., has forced the evacuation of around 100 homes. But the fire may be as much as 70 percent contained by now, with helicopters dropping water from the air and bulldozer crews fighting the blaze from the ground. It remains unclear how the grass and vegetation caught fire in the first place. No injuries have been reported.

Update: NBC Bay Area reports the fire was fully contained as of late Wednesday night. The cause of the blaze is now under investigation.