The medication in question was labeled as simethicone, a drug used to treat gas symptoms, but in fact was the diabetes drug gliclazide, the government said in a statement seen Tuesday.

People without diabetes who take gliclazide develop weakness and lack of coordination in the muscles, mental confusion, sweating and may fall into a coma in severe cases, the government said.

It wasn't immediately clear if the drug mix-up caused the deaths of the two patients -- an 83-year-old man and 86-year-old woman. The government said the deaths will be investigated by coroners.

Three other patients were also treated at the hospital. One remains hospitalized in stable condition, the government said.

Department of Health spokeswoman Diana Kam said Wednesday officials have tracked down 128 of the 151 patients so far.

Other than the two casualties and three hospitalized cases, the exact condition of the remaining patients wasn't clear because they are still being checked, she said.

Police spokeswoman Kelly Chan said without elaboration police are also investigating. It wasn't clear if anyone has been arrested.

Calls to the clinic of the doctor, Dr. Ronald Li, went unanswered.

It wasn't known if Li will face disciplinary action within his profession. Brian Chiu, a spokesman for the Medical Council of Hong Kong, which regulates local doctors, declined comment on the case.