April 8: A gas leak killed two employees at a nuclear plant believed to produce enriched plutonium for Pakistan’s atomic weapons programme.

The leak occurred at the Khushab heavy water plant, which is under military control.

The plant was shut down at the time for annual maintenance, said a statement from the Pakistan Atomic Energy Commission, which evacuated the facility. Officials said the gas leak sparked an explosion and fire but the statement did not refer to either.

The statement said there was no risk to the public outside the sprawling facility. “All necessary steps were taken,” it said, adding that the situation “was immediately brought under control”.

Police near the facility said they were initially advised by plant officials to prepare buses for a wider evacuation. Later, they were told the vehicles would not be needed.

Hamid Mukhtar Gondal, the police chief for the district where Khushab is located, said he was told an accidental blast was caused by an unspecified gas. “The building then caught fire,” Gondal told AP. “Two men suffered burns and died on the way to hospital.”

“The fire has been put out. There is no spread of poisonous gas at all,” he said.

Indian scientists said an explosion at a heavy water facility poses no threat of a radioactive leak in the environment.

In some heavy water plants, hydrogen sulphide is used as a raw material. “Hydrogen sulphide fits naturally with a heavy water plant… not a reactor,” said M.V. Ramana, a physicist and research scientist at the Centre for Interdisciplinary Studies in Environment and Development, Bangalore.

“It could have been stored at high pressure — you can store more material under high pressure — and a leak could explain such an incident,” he said. “The evacuation may be to prevent exposure to the hydrogen sulphide.”

The Khushab nuclear reactor is exactly 10 years old, Experts tracking Pakistan’s nuclear programme have Khushab reactor and the heavy water plant were built with Chinese assistance and is capable of producing 10 to 15 kg of plutonium a year.