One undertaker admitted taking parts from Alistair Cooke's body

The criminal operation saw body parts removed from corpses without the consent of relatives and sold to biomedical companies.

The body of veteran BBC broadcaster Alistair Cooke was among those used.

Brooklyn district attorney Charles Hynes said that hundreds of parts were sold for millions of dollars, and that more people were likely to be charged.

He said the seven, who have not been named, agreed to co-operate in the investigation and entered their pleas in a secret hearing.

The very equipment that they used, the mask and gloves and surgical items were tossed into the bodies

NYC Police Commissioner

Ray Kelly

One of those who pleaded guilty was the undertaker who removed parts from the body of Alistair Cooke, who died in 2004 aged 95, Associated Press reported.

Four other people who have been named - Michael Mastromarino, Joseph Nicelli, Lee Cruceta, and Christopher Aldorasi - on Wednesday pleaded not guilty to charges of illegally harvesting bones and organs from up to 1,000 bodies, and were released on bail.

They could face up to 25 years in jail if convicted.

Mr Hynes said in a statement: "These ghoulish thieves thought they could pull off the crime of the century, stealing bones from the dead, without any thoughts to their victims' families or the transplant recipients who would receive possibly tainted bone and tissue grafts."

Cancerous bones

Prosecutors said they had unearthed evidence that death certificates and other paperwork were changed.

X-ray of corpse showing leg bones replaced with plastic piping

In Mr Cooke's case, his age was recorded as 85 rather than 95, and the cause of death was listed as a heart attack instead of lung cancer that had spread to his bones.

Other evidence includes X-rays and photographs of exhumed corpses showing that where leg bones should have been, someone had inserted white plastic pipes.

The pipes were crudely reconnected to hip and ankle bones with screws before the legs were sewn back up.

New York City Police Commissioner, Ray Kelly, said: "The unspeakable desecration of the bodies - PVC pipe was used to replace bones. Indeed, the very equipment that they used, the mask and gloves and surgical items were tossed into the bodies."

Transplanting tissues such as muscle, skin and bone is common in the United States and the trade in implantable body parts is legal, providing certain conditions are met.