The Delhi Police has registered a first information report against unknown persons in connection with the low-intensity blast that took place near the Israel embassy on Tuesday, PTI reported on Saturday.

No casualties were reported in the incident.

The explosion took place behind the Israeli embassy on APJ Abdul Kalam Road in central Delhi, between a bungalow and the Central Hindi Training Institute. The spot is reportedly not covered by any closed circuit television cameras and is shaded with trees and plants.

The first information report was registered on December 29 at the Tughlak Road police station under Section 3 (punishment for causing an explosion likely to endanger life or property) of the Explosive Substances Act and Section 427 (mischief causing damage to the amount of fifty rupees) of the Indian Penal Code.

While the police had initially zeroed in on a suspect based on closed circuit television camera video from the area, they have not been able to find clearer footage to identify the individual, reported The Indian Express.

The individual, according to the police, “couldn’t speak Hindi properly” and “boarded an auto from Jamia Nagar metro station”. The police are preparing a sketch based on a description of the suspect provided by two auto drivers.

On Tuesday, the police had found a threat letter in the vicinity of the blast site that had been addressed to Naor Gilon, the Israeli ambassador to India. The letter had been allegedly written by a previously unknown group called the Sir Allah Resistance and mentioned words like “Zionists”, “Palestine” and “Gaza”, PTI reported.

Investigators are awaiting the laboratory test results of samples collected from the blast site by the National Security Guard. A broken watch and a few steel bearings were recovered but it is not known whether they had been used to build the explosive device.