The woman was found inside the sociology department teacher's locked house in Chouddapai area, adjacent to the university campus, on Saturday after he was murdered, said Rajshahi Police Commissioner Mahbubur Rahman.

Police had kept mum about arrest though media broke the news. The 11 people shown arrested by law enforcers over the murder also did not include her name.

But Rahman, who is going to be transferred from Rajshahi shortly, admitted arrest of the student while speaking to bdnews24.com on Tuesday.

He said: "The student was found locked inside the teacher's house. She is now at the Victim Support Centre with her mother. We are questioning her too."

The girl was a sociology department student, he added.

After learning the student's name, sociology department Chairman Prof Wardatul Akmam told bdnews24.com that she was waiting for her masters results.

Prof Shafiul Islam died after being hacked by assailants on Saturday afternoon.

Islam used to live alone at the Chouddapai house after his first wife committed suicide and two others divorced him.

His only son, studying at a private university, lives in Dhaka.

Police are looking into the reasons of the student being locked and if she had any link with the murder.

They said the student told them that Prof Islam went out ‘for a while’ locking her inside.

She called the teacher on his mobile phone as he was late, police said adding the phone rang but the call was not answered. On the second attempt she found the phone switched off.

Commissioner Rahman said, “She then informed her friends about the detention over phone and some of them advised her to jump over the boundary wall behind the house. Some advised her to stay inside the house fearing that police could see her jumping over the wall.”

Police said the student came to know from her mother over phone that the teacher was murdered near the house.

Rahman said: “After verification we found her (student) statements true.”

Police came to know that the woman was in a relationship with a former student of the department.

They are looking into the possibility of that student having any connection with the murder.

“We’re (also) seeing whether her personal relation with Prof Islam, if any, had any bearing on the killing,” said Rahman.

A teacher of sociology department told bdnews24.com on condition of anonymity that the female student’s family had good relation with the slain teacher.

“Her parents would go to Shafiul's house,” the teacher added.

The teacher said the student used to attend the Baul song soiree held at the teacher’s house every Monday.