The duo were picked from Tamulpur area of Baksa district taking the number of suspected people picked up by the police to eight, police said. The detained duo have been identified as Sukla Murmu and Safat Murmu.
Two Adivasi Peoples'' Army (APA) members were picked up from a tea garden in Baksa district and four others from Gossaigaon in Kokrajhar district.
The APA had claimed responsibility for the blast on July 10 which resulted in the injury of 93 people and derailment of seven bogies of the train.
The police had initially suspected the hand of NDFB (anti-talk faction) but the outfit later denied its involvement in the blast.