The police say they have arrested 12 of the suspects involved in the robbery in some banks at Offa, Kwara state, last week.
Jimoh Moshood, police spokesman, said phones, SIM cards and Ipads of robbery victims were among the items recovered from the suspects.
Moshood also revealed the identities of those behind the operation which led to the deaths of at least 17 persons, including eight police officers.
Seven suspects had earlier been arrested regarding the incident.
He listed the newly arrested suspects as Adegoke Shogo, 29; Kayode Opadokun, 35; Kazeem Abdulrasheed, 36; Azeez Abdullahi, 27; Alexander Reuben, 39; and Jimoh Isa, 28.
Others are Azeez Salawudeen, 20; Adewale Popoola, 22; Adetoyese Muftau, 23; Aminu Ibrahim 18; Richard Buba Terry, 23; and Peter Kuunfa, 25.
He added that exhibits recovered from the suspects are two Beretta pistols, and twenty rounds of live ammunition.
“The police teams engaged in massive raids of identified criminal spots/flashpoints, stop and search operations, visibility and confidence building patrols, intelligence gathering which led to the arrest of the suspects,” he said in a statement.
“Some of those arrested also involved serious exchange of gun fire between the police and the suspects in their various hideouts.
“All the suspects during investigation confessed to the various criminal roles they played in the commission of the crime, however, investigation is being intensified to arrest other suspects still at large and bring them to justice.”