The Calcutta link in the SIM card network of the Mumbai terrorists has prompted the Special Task Force (STF) of the city police to join the probe and send two officers to Jammu and Kashmir.

The brief for sub-inspectors Partha Mukherjee and Pulak Dutta, who left for Kashmir on Thursday, was to track down those who had called the terrorists in Mumbai using SIM cards bought in Calcutta.

Three of the cards used by the terrorists were traced to Calcutta. The call details of two cards are leading sleuths to Kashmir, Bangladesh, Pakistan and Muzzafarabad in Pakistan-occupied Kashmir.

“We have zeroed in on the locations in Kashmir from where calls were made to the SIM cards before and during the Mumbai siege. The two officers will keep a watch,” said an STF officer.

“All three SIM cards were bought by Indian nationals who are local operatives of terror groups,” the officer added. “The documents they had submitted were all fake.”

The Subsidiary Intelligence Bureau of the central government has learnt that more than 35 SIM cards bought from Calcutta are being used by militant outfits in Kashmir.

“We are trying to find out whether some of these cards were used by the Mumbai terrorists,” said an officer.

As part of the security beef-up following the attack on the country’s commercial capital, the city police have made it mandatory for all cyber cafés to install software that record finger prints and photograph the users.

“The system has already been introduced in central Calcutta. The cyber cafés in other parts of the city will have to follow suit,” said Jawed Shamim, the deputy commissioner of police (detective department).

To crack down on the growing number of hoax callers, the police have asked phone booth franchisees to keep a tab on the users.

“Most of the prank calls spreading panic have been traced to coin booths,” said an officer.