Police sources told IANS on Friday that investigations were in the final phase and raids were on to arrest a few suspects, including a mechanic earlier based at the Dera headquarters on the outskirts of Sirsa town in Haryana.
Punjab Police got the statements of four persons recorded before a Duty Magistrate in Talwandi Sabo in Bathinda district on Thursday regarding the car in which the explosives used in the blast were planted.
Police officials said that the four witnesses had approached police nearly a year after the blast, claiming they could identify the car used in the blast, in which four children were among the dead. They pointed out that the car was assembled at a workshop close to the Dera campus days ahead of the blast.
Punjab Police investigators had hinted that the powerful blast was caused by high-intensity IEDs (improvised explosive devices) packed inside a pressure cooker.
The blast took place just moments after a political rally by Congress candidate Harminder Singh Jassi at Bathinda district's Maur Mandi town, 200 km from here, on January 31 last year.
Jassi is a relative of rape convict Gurmeet Ram Rahim Singh since Jassi's daughter is married to Ram Rahim's son. Jassi was accorded Z category security following the blast.
Deputy Inspector General RS Khatra said witnesses in the case were key to the probe. He said the case would be cracked and more arrests made soon.