A mixture of chemicals was used in the IED (improvised explosive device) which was detonated with a time device, Superintendent of Police (SP) Simardeep Singh said.
Teams of IB and NIA today visited the site of the "low intensity" blast which occurred near Pipli when the bus was on its way to Chandigarh from Sonepat. Around 12 people were injured in the explosion in which IED was suspectedly used.
An FIR has been registered under section 307 of Indian Penal Code, sections 3 and 5 of Explosives Substances Act, section 4 of Prevention of Damage to Public Property Act and section 16 of Unlawful Activities Prevention Act at Police Station Sadar Thana, Kurukshetra, he said.
A Special Investigation Team (SIT) has been constituted under Haryana Additional Director General of Police (Crime) S S Kapoor, he said, adding it has already started its investigation, he added.
Simardeep Singh said the teams of IB and NIA today examined the Haryana Roadways bus and the site at Pipli where the blast took place.
Forensic experts are analysing details to establish the pattern of the Pipli blast with two recent similar incidents at Panipat railway station, he said.
Singh said the central agencies were working in close coordination with Haryana police's SIT.
