New Delhi  - At least 11 people lost vision in one of their eyes after a free cataract surgery went wrong in India's southern state of Andhra Pradesh, news reports said Monday.

The operated eye had to be removed after the patients developed infection during the weekend following the surgery by the private Bollineni Eye Hospital in the Nellore district, the NDTV network reported.

Doctors say the infection may have been due to contamination of drugs or the instruments used.

The condition of 20 other patients who underwent surgery and are currently hospitalized in the southern Chennai metropolis is raising fresh concerns, a report in the Hindustan Times newspaper said.

The eye camp proved to be a nightmare for families of the patients.

One local man who paid 12,000 rupees (257 dollars), was operated on along with those who got the treatment free of charge, his daughter said.

"Doctors say my father may lose the vision in the other eye too if the infected eye is not removed," Dhivya, who uses only one name, told NDTV.

Andhra Pradesh Health Minister Danam Nagender ordered a probe and instructed hospital authorities to stop all such operations.

"Losing eyesight is like losing life. If it is a case of negligence we'll take action," Nagender told reporters.

The hospital authorities have little idea what went wrong but denied negligence by doctors. They said the infection could be from eyedrops rather than the surgery.

"There could be several reasons for the infection and we will know the facts after the testing of the swabs which have already been sent to government labs," N Sai Murali, chief ophthalmologist at the hospital, told the Hindustan Times.

Botched eye surgeries at such free treatment camps in India are not uncommon and are reported by the local media at regular intervals.

In August of last year, 35 people complained of loss of vision after treatment for eye ailments at a free eye camp in the neighbouring Tamil Nadu state.

That incident resulted in a state government ban on free eye-surgery camps. Investigations showed that the hospital had used expired medicines for post-surgery treatment, blinding the patients. (dpa)