Seven funeral home directors linked to a scheme to plunder corpses and sell the body parts for transplants have secretly pleaded guilty to undisclosed charges, prosecutors announced Wednesday.

Brooklyn District Attorney Charles Hynes also announced that a grand jury had voted to bring a new indictment in the case that adds allegations involving funeral homes in New York City and Rochester.

"It is clear that many more funeral home directors were involved in this enterprise," Hynes said.

The seven unidentified directors all agreed to cooperate in an ongoing investigation into what investigators describe as an enterprise to steal bone and tissue from cadavers and sell the material to biomedical supply companies for profit, Hynes said.

All seven entered their pleas in closed courtrooms and their names were withheld. However, defense attorneys said one of them was the director of a funeral home that took parts from the body of late "Masterpiece Theatre" host Alistair Cooke.

Four original defendants in the case were to be arraigned Wednesday afternoon.

Michael Mastromarino, a former oral surgeon, and three other men are accused of secretly removed skin, bone and other transplantable parts from hundreds of bodies without the permission of families.

They were charged in February with counts including body stealing, unlawful dissection and forgery in a case a district attorney called "something out of a cheap horror movie."

All the defendants pleaded not guilty before being released on bail.

Mastromarino, owner of Biomedical Tissue Services of Fort Lee, N.J., allegedly made millions of dollars by selling the stolen tissue to biomedical companies that supply material for procedures including dental implants and hip replacements, prosecutors said.

At the time, prosecutors said they had unearthed evidence that death certificates and other paperwork were falsified. In Cooke's case, his age was recorded as 85 rather than 95 and the cause of death was listed as heart attack instead of lung cancer that had spread to his bones.