Nov. 11, 2014: Indian women who underwent sterilization surgeries receive treatment at the CIMS hospital in Bilaspur, in the central Indian state of Chhattisgarh (AP)

NEW DELHI –  Tainted drugs apparently killed 13 women who underwent sterilization procedures in central India after autopsies ruled out any surgery faults, officials said Saturday.

Amar Agarwal, Chhattisgarh state’s health minister, said a preliminary finding suggested that a poisonous chemical compound, zinc phosphate, got mixed with the drugs at the manufacturing firm whose owner has been arrested. Government laboratories are expected to give a final report by Monday.

Dozens of women who underwent surgeries in the government-run sterilization campaign became ill, and at least 13 died this past week. The others are still being treated.

S. K. Mandal, the state’s chief medical officer, said Saturday that post-mortem reports did not suggest any surgery faults in sterilization procedures.

The doctor who performed the surgeries remains in custody. R.K. Gupta has been accused of performing too many procedures in one day.

Gupta has denied responsibility for the deaths and blamed the medication. However, he said he used to perform up to 10 times more surgeries a day than allowed under government protocols.

On Friday, police arrested the director of the drug manufacturing firm, Ramesh Mahawar of Mahawar Pharma Pvt. Ltd., and his son and charged them with fraud on the complaint of food and drug administration officials.

Outside experts say India lacks oversight in its public health system and that government incentives to undergo sterilization can lead to coercion among poor women. Few Indian men choose to undergo vasectomies, due to cultural taboos.