The other two incidents were the killing of All Bodo Students Union president Swambla Basumatary in 1996 and looting of the 7th Assam Police Battalion armoury at Charaikhola.
Daimary, arrested in Bangladesh and handed over to Indian authorities on May 1, has been in 14 days custody of police in Udalguri district since Wednesday.
Dutta also said that evidences based on interrogation of arrested NDFB cadres "establishing linkages" between the NDFB and local political party Bodo Peoples Political Front (BPPF) were a serious concern for the area.
The SP said that there was no reason to undermine the strength of the NDFB as a militant outfit for a good number of its council members were beyond the security net, and there were inputs that the cadres were operating from several hideouts and making sabotage attempts on railway tracks for massive attacks.
The area had, therefore, been put on maximum alert, particularly railway tracks, trains and important installations, he added.