A senior police official privy to the investigation told bdnews24.com that they were members of the Jamaat-ul-Mujahideen Bangladesh (JMB) and had links with al-Qaeda.



Initially, investigators suspected them to be members of the Indian Mujahideen (IM). But interrogations of two female members of the gang revealed their JMB connection, the police official said.



However, investigators are also probing their possible IM link.



The National Investigation Agency, Special Task Force, the Anti-Terrorism Squad and the Criminal Investigation Department of the West Bengal police are simultaneously investigating the incident.



Around noon on Thursday, an improvised explosive device (IED) went off in a two-storey house at Khargram, in the heart of Burdwan town, about 100km from Kolkata.



Two suspected members of the terrorist group died in the explosion, while another was critically injured.



Two women-- Amina Bibi and Rajira Bibi-- were detained from the house. They were subsequently arrested on Sunday after interrogation.



Police identified the deceased as Shakil Ahmed, a Bangladeshi national, and Swapan Mondal. Another member of the gang, Hasan Saheb, Amina Bibi’s husband, is undergoing treatment at the Burdwan Medical College.



Evidence, including propaganda materials, seized from the house indicated their al-Qaeda links, the official said.



Some pamphlets in Bengali and Arabic contained words and phrases like 'mujahid' and 'salaam to our brothers in Chechnya'. Name of al-Qaeda leader Ayman al-Zawahiri was also found in some pamphlets, the official said.



During interrogation, the two women reportedly also revealed that the bombs made in that house, rented three months back, were meant for terror attacks in Bangladesh.



Sources said police have recovered from the house 55 IEDs, 40kg of explosives, several wristwatch dials, maps, SIM cards, multiple documents of identity, audio CDs of al-Qaeda training modules, half-burnt manifestos extending support to Chechnya rebels, and messages from al-Zawahiri and a mobile phone with jihadi footage.