A teenager was killed after large portions of a three-storeyed house in Baguiati collapsed on Thursday night, police said.

Pictures and what emerged from the debris of the house in Ashwininagar’s Nazrul Park suggested that bamboo poles and wooden planks had been used in place of steel bars and rods to build it.

Dhrubajyoti Mondal, 17, was watching television alone on the first floor of the house when large sections of the second and third floors collapsed.

Mondal was trapped in the debris of the house for at least five hours before rescue teams could reach him, an officer of the Bidhannagar commissionerate said.

Mondal was declared dead at RG Kar hospital.

The city was lashed with rain and the Dum Dum observatory of the Indian Metrological Department recorded 52mm of rain between 5.30pm on Thursday and 5.30pm on Friday.

“The building had been constructed out of poor quality material,” an official of the Bidhannagar Municipal Corporation said.

Krishna Chakraborty, mayor of the Bidhannagar Municipal Corporation, said the house had been built 15 years ago.

Engineers of the civic body went to the site. A preliminary inspection report submitted by the engineers said that instead of metal rods, the walls had been cast around what seemed like bamboo poles and wooden planks, a BMC official said.

“I don’t know why the owner used a combination of wood, bamboo, bricks and cement for the construction. The building had come up long before the corporation was formed and the area was under the erstwhile Rajarhat-Gopalpur Municipality. We have started pulling down the dangerous portions of the building. We are going to check if the building had a building plan at all,” Chakraborty said, terming the incident as “extremely unfortunate”.

Police started an unnatural death case and the civic body started an investigation into the cause of the collapse.

Youngest of three siblings, Mondal lived in the house with his mother Protima and elder brother Kaushik. The family has a kerosene dealership that is housed on the building’s ground floor. The eldest of the three brothers, Krishna, lives and works in Purulia.

“It was raining and I stepped out with my mother to look for houses that we could take on rent. We rushed back home after a neighbour informed us that the house had collapsed,” said Kaushik. He said his brother was looking to enrol for a technical course at a Bangalore institute.

Subho Sarkar, who lives a couple of houses down from the building, said: “I was at a nearby tea stall and heard a crash and rushed to the house. It was raining heavily. I spotted a light on the first floor and heard sounds from a TV. Then both went off. We tried removing the debris and alerted police.”