The summonses to the witnesses will be sent through Ministry of Home Affairs and Ministry of External Affairs, he said.
According to the laid-down procedure, the summonses will be sent to the Indian High Commission in Islamabad which will hand over them to the Pakistani Foreign Ministry.
Sixty-eight people were charred to death in the blasts in two coaches of Samjhauta Express in Panipat on February 18, 2007.
Initially, SIMI activists were believed to be behind the blast, but, later, it turned out to be a handiwork of a group having right-wing leanings.
NIA has filed a charge sheet against several people, including Swami Aseemanand, who recently walked free in the Ajmer Dargah blast case.
It had on June 20, 2011 filed the charge sheet before the special court at Panchkula under various provisions of the Indian Penal Code and Unlawful Activities (Prevention) Act against five accused persons - Naba Kumar Sarkar alias Swami Aseemanand, Sunil Joshi (now dead), Lokesh Sharma, Sandeep Dange and Ramchandra Kalasangra alias Ramji.
The case pertains to the criminal conspiracy which resulted in bomb blasts in the Attari Express (Samjhauta) train near Panipat.
The investigation conducted by the NIA over a period of almost one year established that the entire conspiracy was hatched between 2005 and 2007 by Aseemanand, Joshi and their associates like Ramji, Sandeep Dange, Lokesh Sharma and others at different places including Gujarat and Madhya Pradesh.
The NIA investigation further brought out that Aseemanand was quite upset with the jihadi/terrorist attacks on temples - Akshardham (Gujarat), Raghunath Mandir (Jammu) and Sankat Mochan Mandir (Varanasi).
He used to "give vent to" his feelings while discussing it with Joshi and his associates.
As a result, Aseemanand propounded a "bomb ka badla bomb" theory, according to NIA.
The Samjhauta train was particularly chosen, as most of the passengers who travel in it are Pakistani citizens, it said.
The trail in the case is in advanced stage.
The court proceedings in respect of 249 witnesses have completed out of the total 299 witnesses.
The Samjhauta Express (Attari Express) is a bi-weekly train that runs on Wednesdays and Sundays - between Delhi and Attari in India and Lahore in Pakistan.
(This story has not been edited by Business Standard staff and is auto-generated from a syndicated feed.)