Image courtesy of United Steelworkers.

The United Steelworkers extended a strike at oil refineries Monday to include two BP plants in the Midwest after workers rejected a new contract offer made by Royal Dutch Shell.

The strikes will affect BP’s refineries in Toledo, Ohio and Whiting, Indiana.

“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,” BP said.

The company said it has trained current and former employees to replace the striking workers and operate the refineries until the strike ends.

The United Steelworkers extended a strike called last week against nine facilities after a round of contract negotiations with Shell fell apart last week.

The union said the plants it represents account for nearly two-thirds of refining capacity in the United States.

Shell is representing the oil industry during the negotiations.

Employees at other facilities continue to work under a 24 hour rolling contract extension.

The union’s key demands include wage raises, having employers cover a larger part of health insurance premiums, cutting the number of non-union contractors that can work at a facility, improving safety, reducing overtime and fixing understaffing issues.

“We remain committed to resolving the remaining issues through collective bargaining at the bargaining table,” Shell said.