An official of Kerala’s Department of Factories and Boilers, which investigates industrial accidents, has told The Hindu that an acetylene leak and the “tendency to bypass safety procedures and the overconfidence of workers” may have led to the blast on an Oil and Natural Gas Corporation ship in a shipyard in Kochi.

Five people were killed and seven injured in the blast on Tuesday.

At the time of the blast, workers were engaged in welding around the ship’s potable water tank. “A preliminary inspection points to a leak in the huge quantity of acetylene that was being stored for welding,” Department of Factories and Boilers Director P Pramod said.

Union Shipping and Transport Minister Nitin Gadkari had ordered an investigation into the blast. A team led by the department’s joint director and chemical inspector is conducting the inquiry.

Pramod said that it was likely that a “huge blast wave” occurred due to a momentary explosion, since several of the ship’s compartments were affected. He added that one of the workers said he had left the compartment where the work was being done after smelling acetylene. “They [other workers] said that the explosion happened just as he was returning to the compartment.”

The director said toxic gases are formed when acetylene burns. “This often leads to oxygen being displaced, causing death by suffocation,” Pramod added. He said that the department is waiting for a detailed report on the incident. The autopsy reports are awaited and the investigating team will also speak to other workers, the contractor and the vessel’s owner.