A blockage in a chemical plant processing tower and a worker's failed attempt to clear it were what caused the explosions in northeast China's Jilin Province on Sunday, according to a senior executive with Jilin Petrochemical Company (JPC).

A channel in one of the nitration towers at the benzene production branch was blocked at about noon. A worker tried to unblock it but failed.

It was a botched attempt; that is the company's explanation, according to Zou Haifeng, vice general manager of JPC, a subsidiary of China National Petroleum Corporation (CNPC).

All channels and equipment connected to the plant have been shut down for security reasons, Zou added.

To date, five people are confirmed dead, and one is missing. About 70 people were injured, two seriously. The two, along with 21 others suffering less severe injuries, are still in hospital.

A nurse from Jilin Central Hospital who declined to give her name told China Daily that all the injured were sent to the nearest hospitals beside the plant.

The local government ordered all medical staff in Jilin to be on emergency standby.

JPC is China's first large scale chemical industry base as well as the largest national aniline base.

Benzene, a colorless highly flammable liquid, is extremely toxic before it burns. Burning breaks it down into carbon dioxide and water making it less harmful to humans.

"No toxic gas was detected in the affected district," Zou said.

Local residents and students of two colleges near the chemical plant who were evacuated shortly after the incident have returned to their residences.

An official from Jilin Chemical Industry College, one of the two colleges, said classes resumed yesterday afternoon.

The blast took place at about 1:45 PM on Sunday at a workshop in the No. 101 Chemical Plant.

(China Daily November 15, 2005)