Oct. 25: The National Investigation Agency has unearthed 200-odd cellphone numbers to which calls had been made by suspected Islamic State operative Mohammad Masiruddin alias Musa.

These phone numbers were active in Bengal, Srinagar, Delhi, Chennai and Jharkhand, NIA sources said.

The agency took Musa, a Birbhum youth arrested earlier this year from a train in Burdwan, into its custody recently.

Musa, who was armed with a machete, had allegedly been tasked with beheading a neighbour in Birbhum's Labhpur and raping his daughter to "prove his mettle" to the IS.

The sources said probing each of these contacts would help gauge how deep the IS had penetrated the country.

According to the NIA sources, getting information about 200 cellphone numbers from a single person had boosted the investigation. Most of these numbers were found from contacts on Musa's multiple social-networking apps and the rest were obtained from his phone's call records.

"The fact that half of the numbers we found from him are switched off or are out of use is an indication that our investigation is on the right track," an investigator said.

Musa, the sources said, is the only suspected IS link investigators have found so far between Bengal and the Indian chapter of the terror group.

The sources said although many of the numbers were switched off, technically it was possible to track down the users through the handsets' unique identity numbers. The process is, however, lengthy.

The investigators have found that the calls made by Musa during his stay in Chennai and Bengal were to recipients in Srinagar, Pakur (Jharkhand), Birbhum, Delhi, Chennai and Malda.

From at least four such numbers, numerous calls had been made to Bangladesh. "The owners of these four numbers are untraceable," said an investigator.

Following the trail of these numbers, a two-member NIA team led by an inspector has been camping in Labhpur since Sunday.

"The NIA sleuths first came to Bolpur on October 23 and questioned a dozen people in Labhpur and Nanoor with whom Musa had allegedly been in touch over phone from Chennai," a source said.

The sources said most of the contacts in Musa's phone were locals - neighbours, shopkeepers and relatives in Birbhum.