Authorities in Bangladesh had previously tried to arrest five of the gunmen involved in the Dhaka cafe attack.
Deputy Inspector General of Police Shahidur Rahman said that the attackers were mostly educated and from well-off families.
The 12 hour siege ended with police killing six of the gunmen. A seventh man was arrested, but authorities said that he is only a suspect and they are not sure of his role in the attack.
Most of the 20 people killed by the attackers were foreigners, among them a US citizen.
At least 13 people have been rescued following the raid, according to a Bangladeshi official.
Twenty hostages have been killed in an attack on a cafe in the Bangladeshi capital. So-called Islamic State have claimed responsibility.