MEXICO CITY (AP) — Authorities in Mexico said Tuesday they have arrested an anesthesiologist they blame for an outbreak of meningitis that has killed 35 patients and sickened 79.

Sonia de la Garza, the chief prosecutor in the northern state of Durango, alleged the anesthesiologist used contaminated morphine. It was unclear what charges he faces.

De la Garza said the doctor used “improper procedures” in administering spinal blocks, mainly on pregnant women.

The doctor, whose name was withheld, apparently carried his own morphine from one private hospital to another, spreading a fungal infection that contaminated the medication at the first clinic, authorities said.

The drug may not have been stored properly. Some smaller hospitals or maternity clinics in Mexico don’t have their own dispensing pharmacies or are not authorized to handle controlled medications like opiates, and thus rely on anesthesiologists to bring their own.

De la Garza the morphine was in “multi-use” vials that would be used on more than one patient. She said tests had ruled out the possibility that it might have been contaminated at the point of manufacture.

Authorities also arrested the head of the state health inspection service and one of his employees.

They face charges of failing to carry out their duties and homicide. The director was found not qualified to hold the post, and the employee allegedly falsified an inspection report on one of the four private hospitals, failing to report improper handling or storage of medicines.

It was the latest scandal for Mexico’s woefully under-equipped health care system, which has also had recurring difficulties in supplying medications for children with cancer.

In 2020, 14 people died after a hospital run by Mexico’s state-owned oil company gave a drug to dialysis patients that was contaminated with bacteria. More than 69 patients were sickened in that outbreak.