The Centre on Thursday described the near simultaneous explosions in Pune as a planned and coordinated act.
Union Home Secretary R K Singh said forensic experts were examining the two unexploded IEDs and nature of the four blasts.
"Since the blasts have taken place within an area of 500 metres and within a span of 45 minutes, it appears to be a coordinated act. I am sure there was a plan behind it," he told media persons in New Delhi.
Singh said teams of National Investigation Agency, National Security Guards and Central Forensic Science Laboratory reached Pune early this morning and were examining the explosives.
"They have examined two IEDs which had not exploded. There are three detonators in each and other peculiarity. Investigation is on. We are making progress," he said.
Home Minister Sushilkumar Shinde said there was no update on the blasts so far.
Shinde, who assumed charge of the key department on Wedneasday, held a high-level meeting with top home ministry oficials to review the security scenario in the country, particularly Pune, in view of the blasts.
With inputs from PTI