A video of the lynching went viral on social media
“These Shibir activists have confessed to attacking the bus,” Hathazari police OC Md Ismail said on Saturday.
He said they were arrested in night-long raids on various cottages in the campus.
Fourteen people, including 11 CU teachers were injured, when a bus carrying them was bombed on Sept 10.
The teachers alleged Shibir activists were behind the attack.
Police arrested 25 people on the day of the attack. Five more were nabbed on Friday afternoon.
The university has formed an investigation committee to look into the matter.
Meanwhile, police and CU authorities have filed two separate cases over the attack.