As in prior job actions against other firms, drivers say they are improperly classified as independent contractors, leaving them with fewer workplace protections and lower pay than if they were company employees.

The newly targeted companies could not immediately be reached for comment.

The expanded strike comes as tension at the nation’s busiest port complex is high. A powerful dockworkers union and multinational shipping lines are negotiating a new contract for about 20,000 workers on the West Coast.

Dockworkers have been without a contract since July and management and the union have lobbed public accusations at each other. The barbs have sparked concerns that a lockout or strike could close ports up and down the West Coast.

If truckers set up picket lines at port terminals, it’s unclear if dockworkers will walk off in solidarity.

On Thursday, truck drivers from two other companies-- Total Transportation Services Inc. and Pacific 9 Transportation – walked off the job and set up picket lines at company yards, organizers said.

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