Police detained them on Friday night
A a court on Monday placed prime accused Mizanur Rahman on a seven day remand in connection with the murder of tenth-grader Nila Roy in Savar.
Dhaka Senior Judicial Magistrate Razib Hasan passed the order after Nirmal Chandra Ghosh, sub-inspector of Savar police station, also the investigation officer of the case, produced him before the court seeking a 10-day remand for interrogation in the case.
Opposing the remand, defence counsel submitted a bail petition as well as remand rejection prayer before the court.
The court rejected the bail plea after the hearing.
Police had arrested prime accused Mizanur Rahman along with his two accomplices Sakib, and Joy in Colonel Bricks Field area of Savar's Rajphulbaria around 10pm on Friday, said Saiful Islam, inspector (investigation) of Savar Model police station.
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Police members also recovered a knife that was used in the murder, he added.
Earlier, Rapid Action Battalion (RAB) detained Mizanur's parents -- Abdur Rahman and Nazmun Nahar Siddiqui -- in Manikganj on Thursday night.
Later, they were remanded on Friday under police custody.
So far, six people, including the prime accused, have been detained in the incident.
On September 20, 14-year-old Nila Roy was reportedly stabbed to death by Mizanur after she refused his proposal to have a romantic relationship.
Relatives of the victim said Mizanur of the same locality had been stalking her for long.
On September 21, the victim's father Narayan Roy filed a murder case against Mizanur, his parents, and other unknown assailants at Savar Model police station.