The water tank on the roof of the building at Indra Nagar under which Prerna’s body was found. Picture by Ranjeet Kumar Dey

The seven-year-old girl found dead on Thursday below the water tank of a house at Indra Nagar was allegedly murdered by a youth — an occupant of the same house. Police are on the lookout for him.

The body of the victim, Prerna, was found on Thursday. On Friday, the police said she had been strangulated. They, however, did not reveal the suspect’s name, aged between 20 and 22 years.

Prerna had come to visit her aunt Vimla Devi, who lives in the four-storeyed building on the Indra Nagar road no. 8 under the jurisdiction of Jakkanpur police station. Vimla and her husband Bindeshwari Pandit are teachers in government schools. Along with their three teenaged sons, they occupy a two-room flat on the first floor.

The building has seven other flats, six of which are occupied by tenants. The owner lives on the third floor.

On Thursday morning, Vimla was getting Prerna ready for a bath. She was supposed to return to Barsi village in Bhojpur district, where she lives with her father Vidya Jaikumar, a loco pilot, and stepmother. Prerna’s mother died during her birth.

“One of Vimla’s sons asked Prerna to go to the third floor and ask the landlord to switch on the water pump. She went up and then went to the roof to switch on the pump. She never returned to Vimla’s flat,” said a police officer.

He added: “We searched all the flats and one caught our attention. The rest of the flat was littered but the washroom was clean. We learnt that a youth lived in this flat along with his family. The family is out of town now.”

The police suspect that the youth had lured Prerna into the flat. “But Vimla and her sons were already searching for her. With so many people looking for the girl, the youth must have panicked and killed Prerna. According to the information we have, the youth left the flat at 1.30pm. He took the body to the roof and hid it beneath the water tank. Then he left the building and never returned,” said the officer.

The body was found around 4pm. The post-mortem report on Friday revealed that she was not sexually abused.