Peabody Coal and Arch Coal are being sued.
Members of the United Mine Workers of America filed late Tuesday night a class action lawsuit against the companies in federal court.
The filing, which is on behalf of more than 10,000 retirees and active workers, is an effort to force the companies to pay promised benefits.
The suit claims that Peabody and Arch transferred the health care and pension benefits for active and retired workers to Patriot Coal for the sole purpose of avoiding to have to pay the benefits.
The suit says that the transfer by Peabody and Arch is illegal under the Employee Retirement and Income Securities Act.
Patriot Coal is currently in Chapter 11 Bankruptcy for reorganization.