Calcutta, July 23: A man collapsed on the stairs and died of suffocation after a fire broke out in his fourth-floor flat in Lake Town early today.

His wife, son, daughter and three guests escaped with injuries.

Gautam Dhara, 48, who held a senior position in a private insurance company, may have gone back to check if everyone had escaped from the flat when he collapsed, a neighbour said.

The post-mortem report has said Dhara died of suffocation.

A fire officer said the fire might have started in one of the three ACs in the three-bedroom flat in Avani Oxford around 2am.

Avani Oxford is a housing complex with six G+7 towers. One of the residents said there are 350 flats in the complex.

One of Dhara's school friends and two of his son's friends were in the flat when the fire broke out.

"His wife walked over a window ledge with their five-year-old daughter and entered an adjacent flat," a family friend of the Dharas said. "His son Neil, in his early 20s, suffered multiple injuries while jumping down to a lower floor."

Neil is a law student at Bangalore's MS Ramaiah College of Law.

Neighbours woke up hearing screams. "The flames leapt high and our only aim was to bring people outside to safety," a neighbour said.

Several residents along with guards of the complex used hosepipes to spray water at the flat, Dharamchand Sethia, a neighbour of the Dharas, said.

"The injured people had been evacuated before we arrived. We went and doused the flames," Gour Ghosh, the director of fire services, said.

Dhara's son Neil was taken to Daffodils Nursing Home and later shifted to Apollo Gleneagles Hospitals. Dhara was taken to the nursing home and then to RG Kar hospital.

His friend Manoj Bhat of Ranchi took refuge on a window ledge, the family friend of the Dharas said. "The fire brigade brought him down. He has burns in the ear," he said.

One of Neil's friends is being treated for burns at a private hospital.

An officer of Lake Town police station said: "It seems to be an accident. The exact cause of fire can be determined only after the forensic team submits its report."

Lack of periodic maintenance can lead to AC fires, a CESC engineer said. "If dust accumulates in the AC or if the AC is run continuously for a very long time, it may result in a short circuit and fire."