The IB has advised the Home Ministry to entrust the investigations to the National Investigations agency (NIA) in view of 'prima facie' evidence that the explosions reveal a larger 'trans-regional terror network' involving Jamaat-ul-Mujahideen Bangladesh (JMB), Indian Mujahideen (IM) and Al Jihad, a new outfit with bases in Pakistan.
The IB report says that the two women who were arrested from the house in Burdwan where the explosion took place were both hard core terrorists who were trained in a base in Pakistan's Waziristan province.
"The JMB, IM and Al Jihad are now part of a fraternal terror network that seeks to unsettle South Asia, specially India and Bangladesh," said a senior IB official.
He said Rumi Bibi and Amena Bibi, arrested from the Burdwan house, had joined JMB in Bangladesh ten years ago and had slipped into India along with other activists of the group when they faced a huge crackdown in Bangladesh when Sheikh Hasina assumed power.
Three other women used to work with these two in the Burdwan house that had been turned into a factory for making Improvised Explosive Devices (IED).
"The way they confronted police after the explosions in which their husbands had died proves they were properly trained and motivated, surely indoctrinated," the IB official told bdnews24.com but on condition of anonymity." There were three other women in the team that made the IEDs."
The other three are at large and police is trying to nab them on the basis of description now available from neighbours.
Two other hideouts in Burdwan town have been raided and documents have been seized from one person arrested.
"SIM cards seized from those nabbed suggest long distance calls were made to locations in Kashmir, Mumbai, Dhaka, Chittagong and Chennai. This is clearly pointing to a larger South Asian operation and one not restricted to India," said the IB official.
Al Jihad is a new terror affiliate of the ISIS of Middle East and it is seeking to spot, train and arm recruits for operations in South Asia but many of whom may ultimately be taken to fight the jihad in Iraq and Syria, core areas of the ISIS operations.
The IB official said that his organisation has details of a camp at Shihok in Waziristan in Pakistan's Northwest Frontier Province, where JMB activists from Bangladesh and IM activists from India have been trained over the last two years.
"Those killed in the Burdwan blasts or arrested from there were all trained at Shihok," the IB official said.
He said if the central agencies are allowed a free hand by the West Bengal police, "much more can be found".
But he said the West Bengal police are 'obstructing' the investigations, perhaps for political considerations.
Chief Minister Mamata Banerjee , usually very vocal, has been totally silent over the blasts which adds to her embarrassment after IB's revelations that one of her MPs Ahmed Hassan Imran was a top leader of IM's predecessor SIMI and had strong links with Jamaat-e-Islami in Bangladesh.
For 40 days, she has not made a single statement either over the alleged Saradha funding of Jamaat e Islami or the Burdwan blasts.
"Who says investments don’t come to Bengal! Here we have direct foreign investment in bomb making and arms making," said BJP's West Bengal unit president Rahul Sinha , as he headed for Burdwan to join a party rally on Thursday to push for handing over the investigations to the NIA.
BJP leaders have directly attacked the ruling Trinamool Congress for sheltering terrorists when they were driven out from Bangladesh.
They have even named some Trinamool leaders allegedly sheltering terrorists from Bangladesh.