WHITING, Ind. - More than 1,000 union workers went on strike overnight at the BP refinery in Whiting, Indiana.
Members of United Steelworkers walked off the job at midnight in a dispute over working conditions, wages and benefits.
Hundreds of union members at a refinery in Toledo, Ohio also went on strike overnight.
They join thousands of employees at nine other refineries across the country.
Those workers have been on strike since last Sunday.
Union leaders say contract talks stalled last week and the national bargaining team called for the strike Friday, after the union rejected Shell Oil Company's sixth contract offer Wednesday night.
BP spokesman Scott Dean says replacement workers have been trained to replace the striking employees and keep the refinery running.
Analysts don't expect the strike to have an effect on local gasoline prices.
Dean released a statement that reads "BP remains at the negotiating table and is committed to reaching an agreement that provides good wages while giving management the flexibility it needs to enhance safety, improve efficiency and remain competitive with others in the industry."
Negotiations are still taking place at the national and local levels.
At the national level, the United Steelworkers and Shell Oil Co. are discussing general items affecting all the locals, such as wages, benefits and working conditions. Local negotiations, which began in December, concern issues such as job bidding, local health and safety issues, work hours, grievance and arbitration proceedings, and vacancy filling.