(KRON) -- A crash that broke the trailer of a big rig in half is blocking westbound lanes on Highway 4 in Brentwood Monday morning, according to the California Highway Patrol. The CHP said the crash was first reported by another semi at around 6:12 a.m. Lightning, hail possible Tuesday with rare Bay Area thunderstorm Initial reports indicated that the semi trailer was bent in half resulting in hazards on the road and partial blockage of the right lane. An updated report for the CHP at 6:26 a.m. requesting a heavy tow unit indicated that the trailer had broken in half. By 6:55 a.m., Caltrans was on the scene for road closures. At last report, all lanes were shut down and traffic was being diverted at Sand Creek Road. The CHP said there is no estimated time for reopening the roadway and to expect delays.