Three eastbound lanes and two westbound lanes are closed for the repairs to westbound Interstate Highway 80 just west of the Treasure Island tunnel, according to Caltrans spokesman Andrew Gordon.
The pothole, which is around two feet long and half a foot wide, opened up somewhere in the late afternoon or early evening, Gordon said.
The emergency repairs are necessary because it is big enough to cause problems for motorcycles, Gordon said.
The emergency closure was reported just after 7 p.m. and the CHP is reporting that repairs are expected to be completed by midnight.
Gordon did not know the cause of the pothole.