Part of Highway 330 is shut down between Highland and Running Springs.
Last week's heavy rains and mud slides eroded the soil beneath the highway, causing it to collapse and slide down the hillside.
Caltrans said it is checking the condition of other sections of the road.
Officials said there's a good chance Highway 330 won't reopen until winter is over. However, you can still get to Big Bear using highways 18 or 38.