Four terminals at the ports of Los Angeles and Long Beach briefly closed Tuesday morning after dockworkers honored the picket lines of striking truckers, officials said.
The terminals, however, were up and running by 11 a.m. after an arbitrator ruled that the dockworkers must return to work, spokesmen for both ports said.
More than a 120 truck drivers launched a strike Monday alleging widespread workplace violations against three harbor-area firms that haul freight from the Los Angeles and Long Beach ports.
Strikers vowed to follow company rigs from trucking yards to port terminals. But the demonstration had little effect on cargo flow Monday as picketers stayed at those yards, outside the nation's largest port complex.
On Tuesday picket lines moved to some port terminals, said Barb Maynard, a spokeswoman for the Teamsters union, which is supporting the drivers.
In a brief escalation of the day-old strike, dockworkers walked off the job at the Evergreen, APL and Yusen terminals in Los Angeles around 9 a.m., and at the Long Beach Container Terminal an hour later, port officials said.
But an arbitrator quickly ruled that the dockworkers' contract didn't allow them to leave the job in sympathy with the drivers strike. A similar ruling was issued during a 48-hour trucker strike in April.
Los Angeles port spokesman Phillip Sanfield said the port was operating "near normal" despite minor disruptions from the protests.
If the cargo terminals had remained shut for long or if the closures had spread, trade could have been imperiled at the Los Angeles and Long Beach ports, which handle about 40% of U.S. imports.
Drivers are targeting only trucks from Total Transportation Services Inc., Green Fleet Systems and Pacific 9 Transportation.
The truckers argue that they are improperly classified as independent contractors, leaving them with fewer workplace protections and lower pay than if they were company employees.
The trucking companies have blamed the protests on "outside interests" that want to unionize the drivers.
It is the fourth such protest in the last year. However, unlike previous strikes, drivers have not set an end date for the job action.
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7:05 p.m.: This post has been updated to reflect that the Port of Los Angeles said that picket lines briefly closed an additional terminal Tuesday morning.