During the examination, which started on February 12, questions were circulated on social media platforms on four consecutive days when students appeared for their English, Bengali, history and geography papers.
Sajidur Rahman of Hooghly and two Class 12 students, Sahabul Amir of Malda and Sahabaz Mondal of Bardhaman East, have been arrested. Two Madhaymik candidates have also been held, the CID said in a release.
"The accused had opened a WhatsApp group for sending questions and answers. It has been found that papers were sent out through phone for solving and dissemination of answers after the start of the examination," the release said.