BERKELEY (CBS SF) — The wildfire in the hills along the Oakland-Berkeley border is now 90 percent contained.

Fire officials say cooler weather Thursday and Friday helped crews trying to stop the blaze in which 20 acres have burned.

The fire started on Wednesday around 1 p.m. and hot weather helped fan the flames. The fire is being investigated as arson but there are still no arrests or information on how it started.

Multiple fire agencies who were immediately called to the scene to contain the blaze have left the area and fewer than 50 firefighters will remain on scene.

Grizzly Peak Boulevard, which had been closed between South Park Drive and Centennial Road, has reopened.