Police detained four more students of Rajshahi Polytechnic Institute for their alleged involvement in throwing the principal of the institute into a pond.
Officer-in-Charge of Chandrima Police Station Sheikh Md Golam Mostafa said all the arrestees are activists of Bangladesh Chhatra League (BCL).
"We detained them on Sunday midnight during different drives," he said.
The accused have been identified scrutinising footage of close circuit television (CCTV) camera and information taken from the eyewitnesses, he added.
"The listed accused of the case have not been arrested yet," Golam Mostafa said.
On the other hand, the students are staging protest for the second time to press home their 6-point demand including ensuring overall safety on the campus, arresting the culprits who attacked institute's principal Farid Uddin and providing exemplary punishment to the attackers.
But the number of students is very low than the first day as the students alleged that BCL leaders are threatening them to stop the protest over phone and Facebook.
Meanwhile, a three-member probe body of the Bangladesh Technical Education Department arrived from Dhaka, visited the spot and talked with the students.
The Central Committee has permanently expelled joint general secretary of BCL Polytechnic Institute branch Kamal Hossain Sourav.
A six-member probe committee comprising the Rajshahi Metropolitan Chhatra League visited the institute on Monday morning and spoke to the teachers.
They claimed that no activists from BCL except General Secretary Sourav were in involved in the incident.
On November 2, a group of alleged BCL activists of Rajshahi Polytechnic Institute threw the principal into a pond for not complying with their illegal demand to sit for an examination.
Later, Teachers and students of the institute staged demonstration and formed human chain protesting the physical assault.