FBI agents have reportedly found buckets full of heads, arms and legs, as well as refrigerated heaps of male genitalia and different people’s body parts sewn together while working on a case concerning illegally trafficked body parts.

The officers made the sickening discovery, described as a “horror story”, at a science lab in Arizona.

The Biological Resource Centre in Phoenix – a body donation and tissue bank facility – is being sued by eight families.

The FBI followed a paper trail leading to the centre, run by owner Stephen Gore, which they said was profiting from dismembering and selling remains without donor consent.

The lab was raided by the FBI in 2014, but the testimonies detailing what the agents found have only just been made public because of the lawsuits.

Agents said the bodies had been dismembered with chainsaws and band saws, according to a report by US news outlet KMOV4.

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The lawsuit reportedly alleges: “Pools of human blood and bodily fluids were found on the floor of the freezer.” It said there were no identification tags to mark the corpses.

One agent said he found a “cooler filled with male genitalia”, “a bucket of heads, arms and legs”, and says he saw “infected heads”.

They also described the sight of a small woman’s decapitated head which had been sewn onto a large male torso “like Frankenstein” and hung up on a wall. The creation is reportedly referred to as a “morbid joke” in the lawsuit.

The Biological Resource Centre in Phoenix, Arizona, where body parts were dismembered with chainsaws (Google)

The going rate for a head was said to be $500 (£400). Arms were $750 and a whole body could fetch up to $5,000, according to ABC 15, who cited a federal search warrant.

“This is a horror story. It’s just unbelievable! This story is unbelievable,” Troy Harp, one of the plaintiffs in the lawsuit against the facility, told TV station KMOV4.

Mr Harp had donated both his mother and grandmother to the facility in 2012 and 2013 on the understanding the bodies would be used for scientific purposes.

“Cancer, and leukaemia and whatever else, using sample cells,” said Mr Harp. “That’s what I was told.”

Speaking about what the agents found, Mr Harp said: “Who in their right mind... It’s absolutely gross.”

He also said the use of chainsaws and band saws for dismembering the bodies were “not appropriate”.

The lawsuit alleges the illegal activity at the centre dates back to 2007, according to TV station ABC15.