Claiming "vital" leads in the serial blasts that left 24 dead, Delhi Police has detained six suspects amid clear indications of a similarity with the Ahmedabad blasts in July for which SIMI has been suspected.
Sources in the investigation agencies said that two people have been picked from the walled city and two more from Okhla. The suspects, believed to have links with banned SIMI outfit, were being questioned by joint teams of central security agencies and police.
While two more were also being quizzed, two others detained from Barakhamba Road have been released, they said.
Delhi Police spokesman Rajan Bhagat said "we have got vital leads" but declined to give details saying "we will solve the case soon".
Initial probe pointed to a group belonging to Western Uttar Pradesh behind the five coordinated blasts at Gaffar Market in Karol Bagh, Connaught Place and Greater Kailash. Police teams have been sent to neighbouring UP and Rajasthan.
They said the role of Mumbai-resident Mohammed Subhan Quereshi, suspected SIMI activist, was being probed. Police believe that he could have hacked the WiFI system in Mumbai to send the terror e-mail to various media houses.
Strong similarities were found between the Delhi blasts and the serial explosions in Ahmedabad on July 26 that left 53 dead. Indian Mujahideen, a shadow amalgam of banned SIMI and Lashker-e-Taiba, claimed responsibility for the blasts through an e-mail sent to news organisations around the same time when the explosions occurred.
Sketches of suspected bombers were being drawn by the Delhi Police with the help of five eye-witnesses including a teenage balloon seller, who claimed to have seen them placing packets in the dustbins at Central Park in Connaught Place.
In Mumbai, police said 'wireless fidelity' (WiFi) was hacked by suspected terrorists in Chembur who sent the email to news organisations around the time of the first blast in Delhi.
The Anti-Terrorism Squad (ATS) in Mumbai reached this conclusion after extensive questioning of the owner of the flat from whose IP address the terror mail was sent last evening.
"It is similar to the case of (US national) Kenneth Haywood) and after the preliminary questioning of the flat owner K M Kamath, it is believed that his Internet connection is not secure and is WiFi-enabled, making it easier to be hacked," Additional Commissioner of Police, ATS, Parambir Singh told PTI.
Sarika Kamath, wife of KM Kamath from whose Internet Protocol (IP) address the terror mail was sent, said they have been "victims of technology".
"Hacking has become a terror for common citizens like us. We are innocent and hard-working people," she said.
"We did not feel the need to secure or password protect our Internet connection. But now it has become a necessity for all citizens to secure their connections," she said.
A family, which has migrated from Rajasthan five decades back, suffered the maximum damage as it lost seven of its members in the blast at Gaffar market.
"My family has been completely ruined. What mistake have we done to suffer like this," the weeping middle-aged Guddi said at the Lady Irwin Hospital where a number of blast victims had been brought for treatment.
Till Saturday evening, Guddi's extended family was living on the footpath near the blast site working as rag pickers. Now seven of them are dead, four are battling for their lives and two others are missing.