Investigators on Thursday examined the videocassette of a marriage ceremony that was taking place when a powerful bomb exploded in Varanasi's Sankat Mochan temple to identify the attackers.
They have also picked up some fingerprints from the sites.
At least 20 people were killed and several injured in the explosions.
Investigators have also been able to locate two public telephone booths in the city from where the attackers contacted their operatives after the blasts, official sources said.
The investigators were scouring through the details of the telephone calls made to various places, including Nepal, Dhaka and Pakistan.
They have obtained details about the suspected militants from the owner of a shop, which they had visited before the blasts at the temple and cantonment railway station on Tuesday and left a cooker bomb.
Based on the shopkeeper's version, they have prepared the sketch of the militants. The visuals of the video film of the marriage function was expected to throw light on the identity of the suspected attackers, who carried out the blast in the temple, they said.
Besides going through the video cassette, the investigators were examining a magazine left by a saffron-clad man and a woman wearing a blue sari, near a shop in Godowlia market after planting live bombs near Dashaswamedh Ghat, they said.
They added that forensic tests have been conducted on the fingerprints of the duo obtained from the magazine.