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.

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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.

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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.

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