After the death of 13 women who were undergoing sterilization surgery last week, officials have discovered that the patients may have been administered contaminated ciproflaxacin pills, according to the The New York Times.

The pills, which were a generic antibiotic, were manufactured by Mahawar Pharma, a small company in the Indian state of Chhattisgarh, according to NYT. The firm’s managing director Ramesh Mahawar and his son Sumit were arrested Friday for allegedly defrauding the government.

R.K. Gupta, one of the doctors who performed the surgeries, was arrested last Wednesday. He performed 83 surgeries in one day, according to NPR, even though Indian law limits surgeons to performing only 30 per day.

In a raid of Mahawar Pharma, Indian officials found the pills had been mixed with zinc phosphide, a chemical frequently used as a rat poison, the NYT reported.

Earlier reports said the women may have been sickened by unsanitary conditions at the sterilization camp where they underwent tubal ligation surgery on Nov. 12, CNN reported.

Tubal ligation surgery is a form of sterilization more widely known as “having one’s tubes tied.”

Sterilization is the most common form of family planning around the world, and was used by 223 million women in 2009, according to NPR.

In India, 37 percent of women used sterilization as birth control, but only one percent of men used sterilization, according to NPR.

“I think a woman should have a choice about whether she undergoes sterilization surgery, but it’s similar to abortion. You’re serving the same purpose,” said sophomore Barbara Laurent, an applied legal science major.

According to the Guttmacher Institute, which promotes contraceptive use, the birth control pill and female sterilization were the two most popular forms of contraception in the U.S.

“I think [sterilization] is unethical, but it depends on the situation … If [sterilization] is the cheapest way of providing birth control, then that’s an underlying issue in their healthcare system,” said Chisom Nwaoha, a sophomore psychology major.

The surgeries in India were voluntary. They were performed at a mobile health clinic run by the government, according to CNN, and the women were compensated with 1,400 rupees, or about $23. India implemented a sterilization program in the 1970s to counter its ever-growing population, according to NPR, and has continued because it is a relatively inexpensive way of providing family planning.

According to NYT, officials initially believed unsanitary conditions at the clinics were responsible for the deaths, but linked the tainted pills to them after two men died after taking them for unrelated treatments.

The deaths are a serious concern for American consumers, too. In February, NYT reported that India would face more intense “scrutiny by American regulators for safety lapses, falsified drug test samples, and selling fake medicines.” Margaret Hamburg, the Commissioner of the U.S. Food and Drug Administration, visited Indian drug company executives to share her concerns.