Limon Doria, 'Riyaj', 'Sunny', 'Titon', 'Topu', Imon Hossain and 'Shojib' were picked up during a raid that started around 12:30amon Monday.
Police found sharp weapons and methamphetamine-based Yaba tablets at room 315 where DU Chhatra League Vice-President Arefin Siddique stays.
He was not in the room during the raid and did not respond to phone calls later.
Shahbagh police OC Abu Bakar Siddiq led the raid on a tip-off with the backing of hall provost ASM Maksud Kamal and proctor M Amjad Ali.
"Five outsiders were found at room no 313 while two outsiders were held from room no 314 and 315 respectively," said Maksud.
All those detained were reportedly engaged in the recent incidents of muggings on the campus, said Ali.
He said some already had cases against them.