Bengal STF Seizes Fort William Map, Photo from Pakistani National

Investigators are also examining Khalid's digital trail. Social media chats and phone numbers linked to Pakistan, Nepal, and Sri Lanka were recovered from the duo, the agency said. Some chats and numbers had been deleted. "The deleted chats and numbers are being examined carefully. We are trying to establish the contacts, the nature of communication and whether any information was shared through these channels," the official told PTI.

The probe is focused on whether information related to Army installations was being transmitted across the border and whether the duo are part of a larger network. Investigators suspect Khalid has links with Pakistan's Inter Services Intelligence (ISI). His movements inside India are being scrutinized.

Another line of inquiry is whether information about army movements and infrastructure near the border areas of Petrapole and Ghojadanga was collected. The task force is also examining whether a large operation was being planned ahead of Independence Day on August 15. "Military intelligence agencies have been contacted in connection with the investigation," the official said.

Khalid was taken to a hospital in Habra for a medical examination after his arrest. Both accused were produced before the Barasat court, which remanded them to 14-day judicial custody.