The highway was shut down in both directions shortly before 7 a.m. because of activity involving a man on the Loveridge Road overcrossing, CHP Officer Peter Van Eckhardt said.
Pittsburg police have since taken the man into custody, Van Eckhardt said.
The CHP began reopening the highway at 9:34 a.m., but Van Eckhardt said traffic would likely still be backed up for a while.
