Thirty-two research monkeys at a Nevada laboratory died because human errors made the room too hot, officials for the drug company that runs the lab said Thursday. Animal rights activists complain the company took too long to report the deaths.

Charles River Laboratories Inc. issued a statement saying the monkeys died in Sparks on May 28. The company, based in Wilmington, Mass., attributed the deaths to incorrect climate-control operation.

The company said that it reported the problem immediately to the U.S. Department of Agriculture and the Centers for Disease Control and Prevention, but that it didn't notify the public out of concern for the safety of its 515 employees who work at its labs in Sparks and neighboring Reno.

"Due to the increased level of extremist activity targeting individuals involved in biomedical research in recent months, our first concern is for our employees and the animals we care for at Charles River," the company said.

Company officials also recently met with the USDA to review preventive measures put in place as a result of the accident, the company said. It said that no other primates were affected, and that the public was never in danger.

Kathy Guillermo of People for the Ethical Treatment of Animals questioned the company's claim that it immediately reported the situation to federal authorities because "USDA did open an inquiry when we filed a complaint" in July.

"Their statement about fears for their own safety is absurd," said Guillermo, director of PETA's laboratory investigations department in Norfolk, Va. "They have an abysmal record of animal care. As usual, they are more interested in their reputation than in the animals' safety."

She continued: "That monkeys were literally cooked to death by a heating system failure, as a whistleblower alleges, shows that the facility did not even have a simple alarm system in place to alert staff to the malfunction."

Justin Goodman, PETA's associate supervisor for research, notified the USDA of the group's concerns on July 7 after PETA received an anonymous letter. Robert Gibbens, a USDA official, said in a letter to Goodman the same day that the USDA intended to investigate.

A spokesperson for Gibbens' office referred calls to officials at the USDA's Animal, Plant and Health Inspection Service in Maryland. Officials there did not return a call. Continued...