The University of California, San Francisco (UCSF) apologized for conducting unethical medical experiments in the 1960s and 1970s on at least 2,600 incarcerated men.

The experiments were conducted by two UCSF dermatologists at the California Medical Facility, a prison hospital about 50 miles northeast of San Francisco. The experiments were stopped in 1977 when California prohibited human subject research in state prison, yet one of the dermatologists remains at the university, according to an Associated Press news release.

Experiments included putting pesticides and herbicides on the skin of incarcerated men and injecting the substances into their veins. The men who volunteered were paid $30 a month for their participation, according to a 1977 article in the university’s student newspaper, The Synapse.

UCSF’s Program for Historical Reconciliation released a report earlier this month saying that the doctors who took part in the experiments performed procedures on men who did not have the diseases or conditions doctors were supposedly treating and engaged in “questionable informed consent practices.”

“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.

Howard Maibach, MD, and William Epstein, MD, conducted these experiments. Epstein died in 2006; Maibach still works for the university. Maibach wrote a letter to the university’s dermatology department in which he said he believed the experiments were beneficial to some patients.

“What I believed to be ethical as a matter of course 40 or 50 years ago is not considered ethical today,” he wrote in the letter. “I do not recall in any way in which the studies caused medical harm to the participants.”

Maibach’s son, Edward Maibach, told the Associated Press that the report and press release from UCSF failed to acknowledge the university’s role in the experiments. He claimed the experiments “were known to, and endorsed by, UCSF administrators, including the UCSF ethicist.”

“We are still in the process of considering the recommendations and determining appropriate next steps,” the university said in a statement. “As we do so, it will be with humility and an ongoing commitment to a more just, equitable and ethical future.”