LA Metro resumed all bus and rail service at 5:30 a.m. Sunday after suspending service Saturday night in all protest areas.
The transit agency took the action "to ensure the safety of both the public and LA Metro employees," Chief Executive Officer Phillip A. Washington said.
Metro officials apologized to transit customers who were stranded as a result of the suspension in service.
Local news from across Southern California
"We have taken this action out of utmost concern for the public and our employees during the growing severity of this citywide protest," they said.
Metro officials reissued some buses to pick up stranded passengers in specific areas of Los Angeles, and staffers made the rounds to notify riders of the suspension and encourage them to make other arrangements as a result of the emergency.
"Metro will assist stranded transit riders as best it can given the grave and unexpected nature of this emergency," the transit agency stated.
Metro will provide reimbursement for verifiable replacement trips; to redeem, call 323-GO-METRO.
In Santa Monica, which also ordered a curfew in response to the fourth day of protests in Southern California, the Big Blue Bus routes were suspended until Sunday morning.