The Special Task Force (STF) of the state police seized four more SIM boxes from Jalpaiguri and Alipurduar districts on Friday.

In the past 24 hours, this is the second raid in which the STF has made such seizures.

On Wednesday night, the STF teams had conducted raids in a number of locations of the state, including Darjeeling and Jalpaiguri districts, and had seized as many as 23 SIM boxes, along with several other equipment. Three persons, including a Bangladeshi national, were arrested.

“Three more SIM boxes have been seized from Jaigaon, a the town in Alipurduar district located on the IndiaBhutan border, and one such box has been seized from Jalpaiguri district,” said a source in the STF.

It may be mentioned that A SIM box can hold scores of SIM cards at a time, can route international calls through a card and can help the caller evade international calling charges. Also, different intelligence agencies have found that calls made through such a box are tough to be traced or tapped and can be used by criminals or terror forces.

“Along with the concern about the kind of people who are using the equipment, it also means financial losses to the national exchequer as international call charges can be bypassed,” said a source.

On Thursday, sources in the STF said that they have recovered SIM boxes which have a capacity of 256 SIM slots from seven locations. Added to it, routers and switches, around 400 preactivated SIM cards, WiFi modems, laptop, data cable and some other communication equipment were also seized.

The seizure of SIM boxes from north Bengal, particularly from a bordering area like Jaigaon, has put the police and other agencies on alert.

“This is because a vital defence installation, the Hasimara Air Force Station, is located just 18 kilometres away. Also, the IndiaBangladesh border is not far from Jalpaiguri and Alipurduar districts.It is necessary to find out whether the boxes were used to make international calls,” said an official of a state intelligence agency.