The unlawful use of an ultra-large chlorine container by a rubber plant was responsible for a deadly poisoning incident last week, the work safety watchdog announced on Friday.

The State Administration of Work Safety found that the Lixing rubber plant in Hejian, Hebei province, had installed an oversized container filled with liquefied chlorine in a bid to save on costs.

On the morning of May 13, the tube connecting the container to the chlorine tank truck ruptured, and the resulting chlorine leak led to the deaths of two people and the hospitalization of 25.

Poor regulation, lax emergency response and a lack of safety awareness and professional expertise were among the factors leading to the accident, the administration said.

Local governments were urged to address the illegal use of hazardous chemicals to prevent incidents such as this from happening again.

China saw fewer workplace accidents in the first four months of this year. From January to April, there were no "extremely severe accidents"－meaning those that cause more than 30 deaths, leave more than 100 severely injured or result in more than 100 million yuan ($15 million) in direct economic losses.