A prominent California medical school is apologizing for conducting dozens of experiments on prison inmates in the 1960s and 1970s that it now says were unethical.

Two dermatologists at the University of California, San Francisco — one of whom remains at the university — conducted the experiments of at least 2,600 incarcerated men in the 1960s and 1970s, including putting pesticides and herbicides on the men’s skin and injecting it into their veins.

The experiments were conducted at the California Medical Facility, a prison hospital in Vacaville that’s about 50 miles northeast of San Francisco. The practice was halted in 1977.

"UCSF apologizes for its explicit role in the harm caused to the subjects, their families and our community by facilitating this research, and acknowledges the institution’s implicit role in perpetuating unethical treatment of vulnerable and underserved populations — regardless of the legal or perceptual standards of the time," Executive Vice Chancellor and Provost Dan Lowenstein said in a statement on the school website.

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A wheelchair-bound inmate

A wheelchair-bound inmate wheels himself through a checkpoint at the California Medical Facility in Vacaville, Calif. ( (AP Photo/Rich Pedroncelli, File))

The statement added that the men "volunteered for the studies and were paid for participating."

"But the report raises ethical concerns over how the research was conducted."

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California Medical Facility in Vacaville, CA

California Medical Facility in Vacaville, CA (Google Maps)

The university issued a report earlier this month acknowledging doctors engaged in "questionable informed consent practices" and performed research on men that didn’t have the diseases that the doctors intended to treat.

The San Francisco Chronicle first reported the program’s findings Wednesday.

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Prisoners in California

Prison inmates wearing firefighting boots line up for breakfast at Oak Glen Conservation Fire Camp #35 in Yucaipa, California  (REUTERS/Lucy Nicholson)

The report said further analysis is needed to determine the extent of harms caused to the prisoners as a result of the experiments and what the university should do in response.

The report focused on research by Dr. Howard Maibach and Dr. William Epstein. Maibach continues to work at the university, and Epstein died in 2006. It was not immediately clear whether Maibach would face any discipline in light of the report.

Associated Press contributed to this report