BILASPUR, India - Indian police said Friday they have arrested the head of a drug manufacturing company and his son on suspicion of destroying evidence in the case of 13 women who died after a mass sterilisation programme.

Police said they had taken the two men into custody on Thursday after a raid on their drugs factory in central Chhattisgarh state, where dozens more women were still in hospital after undergoing the surgery. The deaths have triggered widespread criticism of a government-run programme that offers poor Indian women cash incentives to get sterilised, in what activists say are often horrible conditions.

Superintendent Om Prakash Pal told AFP the two men, who ran a drug-making unit in the state capital Raipur, would be questioned on “the quality of drugs they were making”.

Their arrest came a day after police detained the surgeon who performed the operations, R. K. Gupta, who has blamed poor-quality drugs for the deaths.

A local official who spoke on condition of anonymity told AFP that evidence had been burned at the arrested men’s factory.

“We conducted a raid yesterday. We found drugs had been burned in large quantities,” said the official. “Maybe they got scared and knew that we would come calling.”

Gupta operated on 83 women in just five hours on Saturday - spending an average of less than four minutes on each patient.

He has accused the government of making him a scapegoat for the controversial sterilisation scheme, which pays impoverished women 1,400 rupees ($23) to go under the knife.

Although no cause of death has officially been given, authorities speculated that the women had died of septic shock.

The state has launched a judicial enquiry, and Chief Minister Raman Singh said the drugs the women took were being examined.

The state government has banned five drugs used at the camp pending investigations, including an antibiotic and a pain killer.

The victims had suffered vomiting and a dramatic fall in blood pressure on Monday after undergoing laparoscopic sterilisation, a process in which the fallopian tubes are tied.

Human Rights Watch has said health workers in India are coercing women into getting sterilised, under pressure to meet informal targets.

Health Minister Jagat Prakash Nadda denied that India set sterilisation targets for local authorities in an effort to control the growth of its billion-plus population.

But HRW said that although India scrapped national sterilisation targets in 1996, local health workers were still given quotas for the procedure and their jobs were on the line if they failed to meet them.

The United Nations has called for all those responsible for the deaths to be held accountable and said that contraceptive choices should be made “without any forms of incentives”.

“Any laws, procedures or protocols that might have allowed or contributed to the deaths and other human rights violations should be reformed or changed to prevent recurrences,” it said in a statement on Thursday.

Singh has sacked the surgeon who conducted the operations and the chief medical officer who supervised them.

The operations were carried out at a decommissioned hospital on the outskirts of Bilaspur. The actual operating theatre was sealed off on Friday, guarded by about six police officers.

Sterilisation is one of the most popular methods of family planning in India, and many state governments organise mass camps where mainly poor, rural women can undergo the usually straightforward procedure.

A total of 336 people have died as a result of sterilisations in India in the three years since 2010, according to national government figures.