At least 22 elderly people in northern India have lost vision in one or both of their eyes after undergoing free cataract surgery at a state-owned clinic, a government official said Wednesday.

Health Minister Anant Kumar Singh said initial reports suggested they may have gone blind from infections caused by contaminated eye drops used during surgery.

The case marks the second time in three months that mass blindness has been reported after free government surgeries in the impoverished state of Uttar Pradesh. Nine people went blind after treatment in December.

The latest affected group, most of them between 60 to 70 years old, complained of blurred vision, swelling and itching in their eyes within days of surgery, said I.S. Srivastava, a senior health official in Uttar Pradesh.

He said most also had difficulty seeing in their second eye and it was possible that "all of them have lost their eye sight permanently." All of the patients were sent to a government hospital in the northern city of Lucknow Tuesday night, he said.

Doctors at the state clinic have been ordered not to conduct any more surgeries until the inquiry is complete, Srivastava said.

The state's top elected official, Mayawati, who uses just one name, has suspended two doctors who carried out the surgeries.

Nine patients lost their eyesight in December after undergoing cataract surgery at a state-owned eye hospital in Uttar Pradesh's Sitapur district.

Health care in India is often dismal, with private facilities out of reach for most of the poor. Many are forced to go without health care or depend on public hospitals and clinics, which are frequently filthy, overcrowded, and lack full stocks of medicines.