A city court Wednesday sent Hasem Molla to the NIA's custody till Oct 31, and two other key accused to judicial custody till Nov 5 over the Oct 2 explosion in West Bengal's Burdwan district.
Bangladeshi banned outfit Jamaat-ul-Mujahideen is suspected to be involved in the blast.
The explosion in a house in Khagragarh area killed two suspected Jamaat militants - Shakil Gazi and Shobhan Mandal - and injured a third, Abdul Hakim. Six people including two women have been arrested.
The court also directed the state-run SSKM Hospital to submit a medical report by Oct 31 about Hakim who is undergoing treatment there.
"Hasem Molla alias Badru Alam Molla was remanded to the NIA's custody till Oct 31 while two other key accused - Razia Bibi and Alima Bibi - have been sent to judicial custody till Nov 5. The court also directed the SSKM to submit a medical report on Hakim by Oct 31," said public prosecutor.
Taking over the probe of the blast Oct 9 following a directive by the union home ministry, the National Investigation Agency (NIA) secured the custody of the three accused Oct 13. They were presented before the court after the expiry of their custody term.