The moves comes after UNFI officials announced they would permanently replace 72 striking warehouse workers, according to the Teamsters Local Union 117.
The workers went on strike on Monday after rejecting the latest contract offer from the company, but on Wednesday voted to return to work while they continued negotiating a new contract.
They attempted to return to work at UNFI's Auburn facility on Thursday and were told by security officers "they were not on the list," according to the union.
"UNFI misrepresented its position regarding its workers' good-faith offer to return to work. The company's action to replace its employees is retaliatory, unlawful and frankly despicable," the union's Tracey A. Thompson said in Thursday news release.
The union members, who deliver organic produce to area grocery stores, said they don't make nearly as much money as their counterparts at other companies.
The company's contract with the drivers expired in May, but the drivers kept working while negotiations were under way. The union said members rejected United Natural Foods' "last, best offer" over the weekend.
United Natural Foods supplies organic foods to independent markets and large grocery store chains, including Whole Foods, PCC, Metropolitan Market, Safeway, Fred Meyer, QFC and Albertsons.