Most of the 134 victims of a chlorine gas leak accident in Northeast China on Thursday have recovered, local officials said yesterday.

About a dozen remain hospitalized, however.

The emergency aid center in Qiqihar city of Heilongjiang Province received a series of telephone calls for help at about 6 pm on Thursday.

Residents in nearby Gaotou Village said they felt difficulty breathing, and suspected they had inhaled chemical gas.

Some 130 villagers were rushed to hospital for observation and treatment. Examinations showed they were harmed by chlorine - a highly irritating, greenish-yellow gas that can cause dizziness, vomiting, coughing and breathing difficulties.

By about 5 pm on Friday, most of the victims had been discharged by doctors, except 13 patients who still showed signs of respiratory distress, according to the Disease Control and Prevention Center in Qiqihar.

"Some of them still have collection of fluid in their lungs, or pulmonary edema, but they are stabilized," a doctor in the First People's Hospital of Qiqihar said.

The cause of the incident was seven containers of liquefied chlorine gas that were discarded by someone in a pit near the village.

The culprit has yet to be found, officials said.

A local health official said the containers might have come from some local chemical plant or factory that uses chlorine for bleaching, such as a paper mill.

"An investigation shows the containers probably were sold by some factories to a private owner as waste material for recycling," an official, who declined to give his name, said.

The person might have accidentally opened the containers that still contained remnants of liquefied chlorine, he said.

The poison site has been cleared, and the air is now safe, officials said.

Accidents involving chlorine gas have been occurring frequently across the country for the past several years.

Two days before the Qiqihar accident, a truck carrying a 40-ton chlorine tank turned over in Henan, causing a mass evacuation of 24,000 people in 12 nearby villages.

On November 6 of last year, 48 residents living near a paper mill were hospitalized after a chlorine container leaked.

On October 29, a dye-works in Zhouhai, Shaanxi Province sent out chlorine gas after the valve on a container failed. A dozen villagers were sent to hospital.

On August 6, 2003 a discarded container in suburban Xi'an leaked a large amount of chlorine gas, leaving 64 people hospitalized.

(China Daily January 17, 2004)