A strike among members of the United Steelworkers union expanded to two more plants Sunday. Workers at BP’s Whiting, Indiana, refinery and Husky Energy in Toledo, Ohio, joined nine other plants over what they’re calling unfair labor practices.

Talks quietly broke down Friday but the walkout wasn’t announced until Sunday. The refineries affected account for 13% of all refining in the U.S.

The issues include wages, worker safety and reductions in non-union worker contracts. In a statement, the USW said the walkout comes after, "bad-faith bargaining, including the refusal to bargain over mandatory subjects; undue delays in providing information; impeded bargaining; and threats issued to workers if they joined the strike."

Royal Dutch Shell owns most of the refineries involved. Company spokesman Ray Fisher responded, "We regret that we have been unable to reach a mutually satisfactory agreement with the USW prior to contract expiration, we remain committed to resolving the remaining issues through collective bargaining at the bargaining table."

The additional striking workers bring the total to nearly 4,500 nationwide. Most plants are being run with temporary workers at a reduced level. A plant in Martinez, California, owned by Tesoro Corp., will shut down completely. It was already scheduled to undergo an overhaul.

Negotiations had been going on since January, 21^st, but so far no new talks have been scheduled after the latest standoff.