They were picked up by the police from Bongaon-Bagda Road in Bongaon town, located close to the international border, after they were spotted moving around suspiciously on Friday, the official said.
They were produced before a court, which sent them to four days' police custody on Saturday, he said.
The country, they were allegedly planning to travel to after procuring fake documents, is not yet known.
Investigation to bust the fake passport and Aadhaar card rackets, with which the infiltrating Bangladeshis are suspected to have links, is underway.