Three employees of the hotel were also among those killed. (Representational)

Seven people, including four sanitation workers, died of suffocation while cleaning a hotel sewer in Gujarat, officials have told NDTV, in the latest incident that highlights the appalling conditions that they have to work under. The men had entered the septic tank without any safety gear, news agency AFP reported.

The incident took place at Darshan Hotel in Fartikui village of Dabhoi tehsil, about 35 km from Vadodara city.

The four sanitation workers were identified as Mahesh Patanwadiya, Ashok Harijan, Brijesh Harijan, Mahesh Harijan. All of them had been called in from Thuvavi in Dabhoi for the job.

Three employees of the hotel, identified as Ajay Vasava (24), Vijay Chauhan (22) and Sahdev Vasava (22), were also among those killed.

"We are investigating what was the exact gas they inhaled and what exactly happened," said Deputy Superintendent of Police (Dabhoi division) Kalpesh Solanki.

Mahesh Patanwadiya was the first worker to enter the tank but after he stopped responding, Ashok Harijan, Brijesh Harijan, and Mahesh Harijan followed to help him, police officials said. Later, when the four workers did not come out, the other three hotel workers went in but they too fell unconscious inside the tank.

A case has been registered at the Dabhoi Police station. The owner of the hotel has been charged with causing death due to negligence and culpable homicide not amounting to murder.

Scores of sanitation workers die each year from suffocation while removing waste from underground drains in the country, where manual scavenging continues despite laws that ban it.

While government estimates peg the number of manual scavengers in India at anywhere between 14,000 and 31,000, the Safai Karmachari Andolan (SKA), a collective of the sanitation workers, says the figure is closer to 7.7 lakh with nearly 1,800 sewer cleaners suffocating to death in the last decade.

Most sanitation workers are pushed into the profession over generations, finding it difficult to get other work because of caste-based barriers, experts say.

Prime Minister Narendra Modi has often spoken at length about improving the lives of sanitation workers and in a hugely symbolic move in February this year, washed the feet of five of workers to honour staff who cleaned toilets at the Kumbh Mela in Allahabad as news cameras rolled.

(With inputs from agencies)