Fifty-five patients who received the same treatment on their eyes and were given the same drug at a local hospital have come back to the hospital with adverse reactions, with some unable to see.

All the patients had received eye care at the Shanghai No. 1 People's Hospital on Wednesday afternoon.

A primary investigation found they were stricken with a bacterial infection.

The patients have been initially diagnosed with internal eye inflammation. The cause of the infection - whether it was tainted medicine, or improper practice by the medical staff, or infected medical instruments - is still under investigation by the Shanghai Health Bureau, officials said yesterday.

The patients all showed symptoms of red eyes and unclear vision after being given Avastin, an imported cancer medicine that is often effectively used in many countries to treat degenerative eye disorders.

Although approved by the US Federal Drug Administration for treating cancer, Avastin is often used in treating eye diseases such as macular degeneration because it is cheaper than a professional eye medicine but has shown similar results.

The health bureau said it will take days to determine the cause of the infections. If it is hospital's fault, the hospital will definitively give compensation, said a bureau official.

The official said the worse result could be blindness.

Health officials said the medicine was purchased through official channels.

The No. 1 People's Hospital refused all interviews, but Shanghai Daily yesterday managed to talk with one patient by pretending to be her granddaughter.

A local woman in her 50s, surnamed Xu, who accompanied her mother-in-law to the hospital, said they received a phone call from the hospital yesterday morning, and learned that something was wrong with the medicine given one day before.

Xu said that when they arrived at the hospital around 9:30am yesterday, everything had been arranged for them. There were no papers to fill out, no bills to pay and their medical records had been taken away by the hospital.

Xu's mother-in-law, aged over 70 and living in the Pudong New Area, was on a drip when Shanghai Daily visited yesterday afternoon.

"I was awake the whole night. The left eye which was treated at the hospital hurt too much, and I could only walk around the room to distract myself," said the old lady.

She came to the hospital on Wednesday afternoon to cure her left eye, which was unable to see clearly and often dropped tears.

One injection costs each patient 180 yuan (US$26).

But now the eye is not functioning at all, even after receiving a treatment yesterday morning, she said.

The other 54 patients also have been admitted by the hospital. Xu and her mother-in-law met seven others.

Xu said she did not accompany her mother-in-law on Wednesday and had no idea of the exact treatment and medicine used.