Four persons, including a 17-year-old girl, have been apprehended for their alleged role in setting on fire a residential building in south-east Delhi’s Tughlakabad Extension that killed three members of a family, the police said on Sunday, terming the incident a “deliberate act of arson”.

Police said CCTV footage showed the juvenile entering the building with her face masked shortly before the fire erupted on June 12 and then exiting the premises minutes later.

“Based on the evidence collected, the police concluded that the blaze was a deliberate act of arson,” Deputy Commissioner of Police (South East) Hemant Tiwari said.

He said a scooter was set ablaze as part of a conspiracy to settle a “personal dispute”, and the fire engulfed the entire five-storey building.

Earlier on Friday, the police had said the fire may have been sparked by an electrical short circuit.

Police have added charges of criminal conspiracy, attempt to commit culpable homicide, mischief by fire, and house trespass to the FIR that was registered at the Govindpuri police station, the officer said. The juvenile was identified with the help of video footage and apprehended first, leading the police to Sarita, 27, a resident of Girinagar in Govindpuri.

‘Monetary dispute’

The girl told the police that Ms. Sarita instigated her and provided petrol and a matchbox to set ablaze the two-wheeler belonging to Deepak, a resident of the building, “over a monetary dispute”. “She revealed that the conspiracy was hatched at the instructions of Niranjan, 33, and his brother Rajkumar, 27, residents of Navjeevan Camp in Govindpuri, to avenge a personal dispute,” the police said, adding that all four have been held.

Pankaj, 28; his maternal grandmother Shushila Devi, 70; sister Soni, 20, all residents of the building’s third floor, died while his mother, Guddi Devi, 50, and younger sister, Mani, 18, were injured. The incident came in the wake of a massive fire that broke out in south Delhi on June 3, claiming 23 lives.