An animal advocacy group is demanding that four chimpanzees at a medical testing firm be allowed to retire.

The Physicians Committee for Responsible Medicine (PCRM) on July 5 launched a petition and wrote to Dr. Francis Collins, director of the National Institutes of Health, urging him to intervene. The committee asked him to make sure that the animals at the Bioqual research facility in Rockville, Maryland be placed in a federally supported sanctuary in Louisiana called "Chimp Haven."

The chimps were set to be returned to their owner, the New Iberia Research Center, part of the University of Louisiana at Lafayette.

Researchers at the NIH’s National Institute of Allergy and Infectious Diseases (NIAID) and the Food and Drug Administration, have used the chimps — Loretta, Ricky, Tiffany and Torian — to study hepatitis C and malaria, as well as other diseases.

Concern among activists arose after a 1986 video was released showing Bioqual’s chimp and monkey facilities, according to Smithsonian:

Some scientists have argued that, due to their similarity to humans, chimps are essential for research. Last fall, more than 100 scientists, including several Nobel laureates, sent a letter to an NIH committee arguing that losing access to chimps for research would create a “substantial delay” in creating an effective vaccine for the hepatitis C virus.

Nevertheless, the NIH’s demand for ready access to chimpanzees has declined in recent years.

"Much of what I have done over the past years has been research in chimps,” Robert Purcell, 76, who heads the hepatitis viruses section at the NIAID’s Laboratory of Infectious Diseases told Nature. “It’s just a good time now [to retire] as the chimps are essentially no longer available."

Last December, a report from the U.S. Institute of Medicine concluded that most chimpanzee research was scientifically unnecessary and recommended that the NIH sharply cut back on the use of chimps. The agency has since set up a working group to determine whether existing studies should be ended.

Also on HuffPost: