“It is a huge process of eliminating calls routed through the tower from 1-1.30 pm on Friday afternoon. It can lead to the number that was attempting to trigger the second blast or even people monitoring the operations,” said an official.

Sources said details of all calls and SMSs made to and from the recovered SIM card have been obtained from the service provider. The data is being analysed. However, it is still not clear if the failed bomb was to be triggered by a remote phone call or through an inbuilt alarm clock in the cellphone.

“The information lies in the electronic circuit of the phone which was damaged when the bomb was defused. We have to reconstruct it to provide a clear answer,” said explosives experts.

Officials are not ruling out the possibility that fake SIM cards may have been used too. The police are also tracking the International Mobile Equipment Identity (IMEI) numbers of the two Nokia handsets used in the bombs. Using the IMEI number, officials have found that one phone was bought in West Bengal.

The IMEI number (35393801248899) of the cellphone used to explode the first bomb has also been salvaged. The details of the SIM card destroyed in the blast have been obtained through this number.

“The investigation is yet to focus on the questioning of witnesses and suspects. The focus is on processing the technical information as fast as possible,” said sources.

Meanwhile, a bomb squad and forensic team from the National Security Guard (NSG) in Delhi visited the Mecca Masjid today. The team found another cellphone and some bomb shrapnel in the Wazu Khana, or the water tank, where the explosion occurred.

“We are trying to confirm whether this phone was part of the detonation units, or belonged to a worshipper,” said Hyderabad Police Commissioner Balwinder Singh. According to officials, an eight-member NSG team is probing the blast.