Port truck drivers at a Carson-based company announced Monday they will again walk off the job to protest what they describe as wage theft and unfair working conditions.

Drivers with Pacific 9 Transportation will begin pickets at 6 a.m. Tuesday at the company’s yard in Carson, then spread to marine terminals at the Port of Long Beach and Port of Los Angeles, according to the International Brotherhood of Teamsters, which is trying to win unionization for the drivers.

The action announced Monday is the sixth strike truckers have waged in their attempts to become employees of the companies. The last strike involved four companies, including Pac 9, and ended after a week of protests in early May.

It was not clear how many truck drivers would participate in the strike announced Monday, but union officials said it would last “indefinitely.” Port drivers are also in the midst of bringing their grievances to the California Division of Labor Standards Enforcement, union officials said.

At a press conference Monday in downtown Los Angeles, truckers described working conditions as intolerable at Pac 9. The cost of maintaining trucks is high, and the drivers do not receive benefits other workers enjoy.

“I’ve been a port truck driver for five years and I have never worked for a company that treats their workers like Pac 9,” contract driver Pedro Martinez said. “The company refuses to recognize us as employees, refuses to provide us with safe and reliable trucks and refuses to improve our work environment.”

Representatives from area trucking companies, however, have said that most truck drivers want to remain independent for the flexibility and the ability to own their own small businesses.

Truckers hoping to unionize have been battling for several years over their classification as contractors. The acrimony began in 2012 when truckers sued their bosses for wage theft and job misclassification as independent contractors. The following year the truckers began strikes at companies that have also included American Logistics International, Green Fleet and Total Transportation Services, Inc.