Detective Branch (DB) of police has been put in charge of the investigation into Sohagi Jahan Tonu's murder inside the Comilla Cantonment.
"The case has been passed over to the Detective Branch to speed up the investigation," Comilla Superintendent of Police Shah Abid Hossain informed reporters on Saturday.
Earlier in the day, RAB interrogated the family members of Tonu, the Comilla Victoria Government College student who was raped and murdered last week.
A RAB-11 team picked up Tonu's mother, brother and cousin on Friday midnight from their Mirzapur residence in Muradnagar upazila, their neighbour Humayun Kabir said. They were sent back in the morning.
Cantonment Board officials had taken away Tonu's father Yaar Hossain and elder brother on Friday afternoon, Kabir added.
He said two men from the neighbourhood had accompanied Tonu's family to the RAB offices.
The elite force's Comilla Crime Prevention Company-2 commander Maj Khorshed Alam said they had brought in Tonu's mother and relatives to get more information about the murder. “We dropped them at their cantonment residence later,” he added.
Second-year history student Tonu was sexually assaulted and murdered on March 20 inside the cantonment area when she was returning home from her part-time job as a private tutor. Her father filed a case with police the next day without naming anyone.
The incident has triggered mass protests around the country. Thousands of Victoria College students have been staging demonstrations for three straight days demanding punishment for the killers.
Meanwhile, the army on Friday said it would assist the police investigation into the murder.