Investigators have been hunting the CNG-run auto-rickshaw and its driver which carried Tasfia Amin from Chittagong city's Golpahar area on May 2 after coming out from city a restaurant.

Tasfia, a ninth-grader of Sunshine Grammar School and College in Chittagong, was found dead on the concrete blocks at embankment of Karnaphuli River in the city's Patenga Naval area on May 3.

After the recovery of the body, her father Md Amin identified it and told police that she had been missing since Shab-e-Barat (May 2) evening, after leaving her OR Nizam Road residence to meet a friend.

The victim's father later filed a murder case accusing six persons including the friend, and another six unnamed, with Patenga Police Station in this connection. Police later arrested the main accused, who is a ninth-grader of Bangladesh Elementary School.

After the arrest, the accused told police that he met Tasfia in a restaurant in Golpahar area that evening, and later helped her rent a CNG-run auto-rickshaw to go home as her family was looking for her.

“Thay have been hunting the CNG-run auto-rickshaw which carried Tasfia from Golpahar area,” Assistant Commissioner (AC) Jahedul Islam of Chittagong Metropolitan Police (CMP)'s Karnaphuli Zone told The Daily Star.

“We have collected several CCTV footage of the auto-rickshaw from different locations including Patenga area, but the number plate of the vehicle was not clear in them. Now the videos are being analysed by experts to find out the number,” AC Jahed added.

Investigators said Tasfia boarded the CNG-run auto-rickshaw around 6:45pm.

“We have been working to find out answers of some questions, and the CNG driver is now a crucial person of interest in the investigation. We have identified the other CNG and its driver which was boarded by Adnan after seeing off Tasfia,” said the AC.

Once the driver who carried Tasfia is detained, it will be known how the girl reached Patenga, he added.

Mentioning that viscera samples from the victim were sent for examination, AC Jahed said, “We are waiting for the post mortem report. We have asked for examination of vaginal swab and chemical analysis to know whether she was raped or poisoned.”

“We hope the report will be received soon and once we get the report, it would be clear how she died,” added the AC.

Investigators said Tasfia's iPhone and gold ring also went missing. The iPhone had no SIM cards.

Earlier on Sunday, a Chittagong court sent the prime accused to Tongi Kishore Unnayan Kendra (Juvenile Correction Centre) in Gazipur and ordered police to quiz him in front of the director of the centre. The directive came after police sought a 10-day remand for him in the case.

Assistant Commissioner (AC) (prosecution) Kazi Shahbuddin of CMP said the court has asked the investigation officer to submit the interrogation report within 10 days.

Meanwhile, police sources said Tasfia's father Md Amin, who is a businessman, is accused of several cases filed in connection with drug peddling in Teknaf.

Police have quizzed victim's parents considering their background, said AC Jahed.

Along with police, Police Bureau of Investigation (PBI) is also investigating the case.