Delhi: Four labourers and their supervisor died of suspected asphyxiation after they went inside a 14-foot-deep manhole at Nandgram’s Krishna Kunj colony in New Delhi without any safety gear on Thursday afternoon.

The workers were trying to connect the one-and-a-half-foot-wide manhole to an under-construction sewer line in the area.

The work was being carried out by the UP Jal Nigam through a private contractor under the Atal Mission for Rejuvenation and Urban Transformation (AMRUT) scheme. An FIR has been filed and four Nigam officials suspended.

The victims have been identified as Damodar, 40, Horil, 35, Sandeep, 30, Shiv Kumar, 32, and their supervisor, Vijay Kumar, 40. They were all from Sighia block in Samastipur district of Bihar. Sandeep, Shiv Kumar and Vijay were related to each other.

The tragedy follows a series of such deaths in Delhi and its neighbouring cities. The last major incident happened last September, when too five men had died while cleaning a sewer in West Delhi’s Moti Nagar.

An FIR has been registered against the contractor, private firm EMS Infracon and Jal Nigam officials, police said.

The firm has been blacklisted and barred from participating in any government tendering process. Four Jal Nigam officials — Jal Nigam general manager (Yamuna pollution control unit) Krishna Mohan Yadav, executive engineer Ravinder Singh, assistant engineer Praveen Kumar and junior engineer Azamat Ali — have been suspended.

Principal secretary Manoj Kumar Singh said, prima facie, the workers died due to negligence towards safety measures and dereliction of duty by Jal Nigam officials and the private firm.

According to locals, the four workers went inside the manhole around 1.30pm on Thursday and the supervisor went in last.