LITTLE ROCK, Ark. (AP) — Inmates at a northwest Arkansas jail have been prescribed ivermectin to combat COVID-19, despite warnings from federal health officials that the antiparasitic drug should not be used to treat the coronavirus.

Washington County’s sheriff confirmed Tuesday night that the jail’s health provider had been prescribing the drug. Sheriff Tim Helder didn’t say how many inmates at the 710-bed facility had been given ivermectin and defended the health provider the jail uses that has been prescribing the medication.

“Whatever a doctor prescribes, that is not in my bailiwick,” Helder told the Washington County quorum court, the county’s governing body. Helder did not immediately respond to a call from The Associated Press, and a spokesperson for the sheriff’s office referred questions to Karas Correctional Health, the jail’s health provider.

It’s not clear what information inmates who were prescribed the drug have been given about it, including warnings that it isn’t approved to treat COVID.

The U.S. Food and Drug Administration has approved ivermectin in both people and animals for some parasitic worms and for head lice and skin conditions. The FDA has not approved its use in treating or preventing COVID-19 in humans.

“Using any treatment for COVID-19 that’s not approved or authorized by the FDA, unless part of a clinical trial, can cause serious harm,” the FDA said in a warning about the drug.

Health officials in Arkansas and Mississippi this week warned people to not take the veterinary formulation of the drug after seeing an uptick in calls to their poison control centers. The drug has been touted by some Republican lawmakers in Arkansas as a potential treatment for COVID.

Eva Madison, a member of the quorum court, called the use of the drug on inmates “disturbing,” noting that they’re not in a position to seek a second opinion from physicians about its use.

“Are we allowing him to effectively experiment on our detainees at our jail with no oversight?” Madison said.

Karas Correctional did not immediately return a message left Wednesday morning. Helder said Karas informed him of the drug’s use in July, the Northwest Arkansas Democrat-Gazette reported.

Helder said Tuesday night that the jail has had zero inmate deaths from the coronavirus, and jail officials said inmates have also been offered the Johnson & Johnson vaccine.

The American Civil Liberties Union of Arkansas criticized the drug being prescribed to inmates, citing the FDA’s warnings about the drug. The group said it was seeking additional records about the drug’s use from the sheriff’s office and from the health provider.

“They need to stop this practice immediately,” ACLU of Arkansas Executive Director Holly Dickson said.