Two men, part of a group of labourers putting up hoardings at the Alipore zoo, were electrocuted on Thursday morning.

A third was injured and is in hospital. An official of the hospital said his condition was critical.

The deceased have been identified as Tarani Ghosh, 31, from Murshidabad, and Pradip Das, 45, from Odisha.

The men were electrocuted around 11.30am, opposite the elephant enclosure. The chain of events leading to the deaths was not immediately clear.

The group had been camping on the zoo premises for several days, said zoo officials. “Continuous process industries and industries with in-house workers” are exempt from the lockdown curbs, according to the state government guidelines.

The team was working for a contractor, who had been hired by an outdoor advertising agency, sources at the park said. “The labourers were electrocuted while doing some maintenance work. Two of them were declared brought dead at the hospital. The third is undergoing treatment,” a police officer said.

An official of the Delhi-based outdoor agency said: “From what I have gathered, the men were not erecting a hoarding on Thursday. The accident happened when they were collecting materials lying on the ground….”

Asked if safety protocols were followed, the official said: “It is not possible for us to keep tabs on the minute details of every project. The contractor had hired the men.”

The zoo is shut for visitors because of the pandemic. Only a handful of keepers and guards are now engaged, mostly for daily maintenance.

“There was no keeper or guard at the spot at the time of the incident,” zoo director Asis Kumar Samanta said. “I was alerted around noon. The men were shifted to hospital immediately on a zoo vehicle.”

“We have started a probe into the incident,” said VK Yadav, member-secretary, Bengal Zoo Authority.

“Electrical engineers will visit the spot tomorrow to find out how the labourers came in contact with a live wire,” said a zoo official.

“Prime facie, it seems to be a case of electrocution. The zoo authorities will conduct their own probe,” a police officer said. Asked why the police were not registering a case of negligence suo moto, the officer said: “Someone has to first allege there was negligence.”