The 900 detainees were questioned over various offences ranging from drug possession to traffic violations.
Unknown jihadists attacked a luxury hotel in November, killing 20 people including many foreigners.
The attack on the luxury hotel in Mali's capital killed 20 people.
Twenty people plus two gunmen died in Friday's assault on the Radisson Blu hotel.
Mokhtar Belmokhtar has been a key figure in insurgencies across North Africa.
Sahara-based militants says its fighters laid siege to the Radisson Blu hotel in Bamako