BREWER – A dozen drivers who deliver packages on behalf of DHL on Monday morning returned to their jobs with an independent contractor accused of violating their labor rights.

It may be a few months, however, before the Teamsters labor union and Rydbom Express iron out an employment contract for the drivers, who had been out of work since March, according to Teamsters officials.

Union leaders and a few politicians stood by outside Rydbom Express’ offices on Parkway South as the 12 drivers, half of whom were wearing yellow DHL shirts, reported to work at 8:30 a.m.

The federal National Labor Relations Board has issued a complaint against Rydbom Express, a Harrisburg, Pa.-based company accused of violating labor laws when it was given a contract earlier this year to handle DHL’s local operations. The drivers had worked for Black Bear Courier of Orono, which lost its Brewer and Presque Isle contracts with DHL after its employees voted in January to join the Teamsters. DHL has denied that the vote had anything to do with the contract.

According to an amended charge filed earlier this month with the NLRB, Rydbom Express is accused of having “interrogated prospective employees regarding their union activity, threatened prospective employees, made statements to the effect that unionization is futile, and created an impression of surveillance.”

Kathleen McCarthy of NLRB’s Boston office said Monday a hearing on the complaint has been scheduled to take place in front of a judge on Aug. 2. A location for the public proceeding has not yet been selected, she said.

“We’ll schedule it someplace in the Bangor area,” McCarthy said.

No complaint is being pursued against Granite State Express, the Portsmouth, N.H., company that took over DHL’s deliveries out of Presque Isle, because all but one of the 25 former Black Bear Courier drivers there have been rehired or found jobs elsewhere, Teamsters officials have said.

James Carson, president of Teamsters Local 340 in South Portland, said Monday that though the drivers have returned to work, it likely will take several months of negotiations for Rydbom and the Teamsters to agree on an employment contract. One issue likely to be discussed is back pay that Rydbom allegedly owes the union drivers, he indicated.

“Stayed tuned, because this is a long way from over,” Carson said. “It’s quite a game, I tell you, and it’s being played nationally.”