The exams began at 215 centres across the country at 10am on Friday
The body was recovered on Monday morning, said OC Sajjadur Rahman.
The victim, Parvez Ahmed, 20, was a second-year student in the Social Welfare Department and worked part-time at the local Meghna Workers Multipurpose Association.
Police have detained three coworkers, Jahangir, Shohag and Sharmin, for questioning.
Parvez went missing after he was called away around 8am on Sunday to provide an explanation for the association’s budget, said Rahman citing the victim’s family.
Locals called the police on Monday after finding the body floating in the river.
There were no signs of injury on the body, Rahman said.