The Darjeeling district police also recovered two unexploded bombs and sophisticated timing devices from the house that was rented by the victims.

"We received information around 1.10 pm that there had been a gas cylinder explosion in Pradhan Nagar in the Champasari area. On reaching there, we found two unexploded bombs with detonators that could be programmed to go off in anything between eight minutes to 194 days," Superintendent of Police P Rahul Srivastav told The Indian Express.

Though Srivastav said that the deceased have not been identified, sources in the police said that one of the deceased was Tsering Lepcha of Sikkim.

After questioning the landlord of the building, which was rented by the deceased, it was found that the woman killed in the blast was the sister of one of the victim and used to frequently visit the place.

"They had rented some rooms in the building and had introduced themselves as students. At the moment, we can't say if they belonged to any militant group," Srivastava added.

In spite of the police being tight lipped about the incident, sources said that two mobile SIM cards have been recovered from the blast site. While one belongs to an Indian mobile service provider, the other is of Nepalese operator Mera.