A cement mixer broke down while driving on northbound Interstate 680 on Tuesday afternoon, blocking the two left lanes in the process and creating a traffic headache, the California Highway Patrol said.

The truck stalled around 2:35 p.m. near the Ygnacio Valley Boulevard exit, according to the CHP. A severe traffic alert was issued at 3:11 p.m., indicating the two left lanes would remain closed indefinitely while crews tended to the truck, the CHP said.

The lanes were shut down until around 4 p.m., and traffic was backed up to the Diablo Road exit, the CHP said.

The CHP did not have any information on what may have caused the truck to become disabled.

Rick Hurd covers breaking news. Contact him at 925-945-4780 and follow him at Twitter.com/3rdERH.