An illegal leather-cutting unit and godown on the first floor of a residential building in Tiljala caught fire early on Sunday. Four of the six workers sleeping in the 3,000-sq-ft unit were injured.

The residents, alerted by a blast, managed to leave the building. Eleven fire tenders took almost three hours to douse the flames.

A blaze in an illegal sweatshop at 33C Topsia Road, about 500 metres from the site of Sunday’s fire, killed nine young men in November 2006.

Alert residents of 18A/E Kustia Masjid Bari Lane and timely arrival of fire tenders prevented a rerun of the tragedy. Several cartons of leather wallets ready for shipment were charred.

The unit caught fire around 3am. “Had it not been for the blast, we would have slept on and the fire would have caused much more damage. I rushed to the balcony and saw the floor below was ablaze. The flames were nearly touching our floor,” said a tenant on the second floor.

After evacuating his family, he rushed back to the first floor. “The workers trapped inside the leather unit were desperately trying to come out but could not access the key to the locked gate,” added the tenant.

He and some other residents of the building broke down the door to help the workers escape.

The injured — Javed Hussain, 28, Mohammad Wahid, 30, Fajir Alam, 20 and Mohammad Naushad, 28 — were taken to hospital.

The cause of the fire could not be ascertained. The fire department is contemplating action against the owner of the unit.

It had “machinery, electrical fittings and generators but no fire-fighting arrangement”, said Gopal Bhattacharjee, the director-general of West Bengal Fire and Emergency Services.

Sharafat Hussain, son of landlord Liaqat Hussain, said the unit belonged to Atiullah Khan. Residents said the fire was waiting to happen. They had complained to the landlord about the unit several times but no action was taken.

“The unit was stacked with leather and other inflammable goods. Work would go on round the clock. We felt unsafe as scores of people would move in and out of the building,” said a resident of the second floor.

Sharafat, who stays in the building with his father, said: “The leather unit is six years old. In this area, it is a common practice to let out space to sweatshops. We get good money by renting space to commercial units.”