The suspect, identified as Hamid Mondal, was arrested from his rented accommodation in a housing complex in Burdwan town late on Thursday, according to police sources.
Investigators are now analysing digital material and documents recovered from him.
Mondal was produced before a court in Burdwan on Friday as the investigation continued into his alleged activities, contacts and possible links with other suspects.
JeM links under investigation
Police suspect Mondal of having links with JeM, a Pakistan-based banned terror organisation.
Investigators also believe he was closely associated with Sajjad Bhat, who has been described as an alleged mastermind of the 2019 Pulwama terror attack.
The Pulwama attack took place on February 14, 2019, when a suicide bomber rammed an explosives-laden vehicle into a bus carrying Central Reserve Police Force personnel in Jammu and Kashmir. Forty CRPF personnel were killed in the attack.
The alleged JeM connection is now a key part of the Bengal STF investigation, which is also seeking to establish whether Mondal was acting alone or had links with a broader network.
Why was CM’s movement being tracked?
According to police sources, investigators found material on Mondal's mobile phone and other documents that suggested he had been collecting information about West Bengal Chief Minister Suvendu Adhikari.
The material reportedly included details concerning the Chief Minister's movements and programmes.
Investigators are examining why such information was being gathered and whether it was connected to a potential attack.
Details of Adhikari's movements were among the information allegedly recovered from Mondal, sources in the state police said, adding that investigators are examining whether the surveillance formed part of a possible terror plot.
Police sources have not publicly established that an attack was planned, and the investigation remains at the stage of determining the purpose behind the alleged surveillance.
Suspect staying in Burdwan for months
According to police, Mondal had been living in the rented flat for around two to three months.
Investigators suspect that he had chosen the accommodation to avoid detection by law enforcement agencies.
The STF is now examining his communications, contacts and other material recovered during the operation.
Investigators are also looking into whether additional people were associated with his alleged activities.
The arrest has brought the focus of the state police's counter-terror investigation to Burdwan, while the alleged links between Mondal and the wider JeM network remain under scrutiny.
Pakistan links
Some reports have also claimed that investigators suspect Mondal had connections with Pakistan-based handlers and that he may have received training there.
These claims have not been publicly established by the police in the official details released so far.
According to reports, the investigation is focused on determining the extent of Mondal's alleged association with JeM, his contacts and the purpose of the information allegedly collected about the Chief Minister.
The police are also expected to examine digital evidence for indications of communication with other members of the alleged network.
Explosives seizure adds another security concern
The arrest comes amid a separate explosives seizure in Burdwan's neighbouring Birbhum district.
According to the information provided by police sources, a large quantity of explosives was recovered from an abandoned house in the Nalhati area following a tip-off.
The seizure reportedly included more than 800 kg of ammonium nitrate, over 1,200 gelatin sticks, 105 detonators and 36 detonating fuse coils.
The explosives recovery is being investigated separately, and no direct link between that seizure and Mondal's arrest has been established in the information available.
Probe into wider terror network continues
The Bengal STF is now examining the suspected operative's network and alleged activities as investigators seek to determine whether the surveillance of Adhikari was part of a larger conspiracy.
The material recovered from Mondal's phone and documents has become central to the probe, with investigators assessing the nature of his alleged communications and contacts.
Police are also looking into the possibility of other individuals being linked to the case.