Union workers at Marathon Petroleum's refinery in St. Paul Park decisively rejected the company's latest contract offer, five months after they went on strike.

The contract offer was made on March 1, and the union has been negotiating since.

Marathon billed the offer as its "last, best and final" proposal, according to Teamsters Local 120, which represents 200 workers at the refinery.

The union asked Marathon to clarify several points made in the offer, said Scott Kroona, business agent for Teamsters 120.

"We have gone back and forth with them, and they have given us some answers but not all," he said. "This has been going on a long time, so we thought it was a good time to let our members be heard. ... I think our members made their voices loud and clear."

In a statement, Marathon said it continues to believe the March 1 offer "is a good, fair offer focused on safety, the refinery's continuous improvement and fair wages for our employees."

The union maintains that Marathon's contract offer would cost it more than 40 jobs, with Teamster workers being replaced by employees of non-union contractors. The move would compromise plant safety, the union says.

Marathon denies that safety claim and has said its proposal would lead to only one job being contracted out.

Marathon has continued operating the refinery with management employees from St. Paul Park and its other refineries. The Teamsters say they are now locked out of their jobs after offering to return to work shortly after the strike began.

Marathon has dismissed the notion of a lockout, saying the union remains on strike.

Marathon said it is "in the process" of hiring additional permanent employees at the refinery. Kroona, however, said permanent replacements cannot be hired while the union's unfair labor practice charges against Marathon are pending before federal labor regulators.

He said the union last met with Marathon last week.

"We have notified the company we are available to meet and to get back to the table to get a deal done," he said.

The company said in the statement that it remains "interested in reaching a mutually satisfactory agreement with the Teamsters Local 120 and will continue to respond ... to correspondence we receive from them."

Findlay, Ohio-based Marathon, the nation's largest oil refiner, bought the St. Paul Park refinery in 2018. The property was part of Marathon's $23 billion buyout of San Antonio-based Andeavor.

Marathon Petroleum's corporate predecessor, Marathon Oil, co-owned or owned the St. Paul Park refinery from 1997 to 2010. Marathon, one of two oil refineries in Minnesota, is the prime gasoline supplier to Speedway stations in the Twin Cities.