Encouraged by the breakthroughs in the probe into the July 11 blasts, Police Commissioner AN Roy on Sunday said there had been "some positive developments" and predicted more arrests would be made "very soon".
Police and the Anti-Terrorism Squad (ATS), which was criticised for both failing to avert the attacks that killed 200 people and the delay in making a breakthrough in the probe, got a shot in arm with the arrest of three suspects on Thursday, almost 10 days after the blasts.
Roy said, "Police were taking steps very carefully. We do not wish to create extra hype about the suspects. We have held them on suspicion and never said they are the accused in the case."
He said there was no direct material to establish their links with the attacks, but the three arrested men - Kamal Ansari, Khalid Ahmed and Mumtaz Chaudhary - had links with the Lashker-e-Taiba and may be remotely associated with the blasts.
"Definitely these people are involved in a LeT module. We have information that these people sent men for LeT training. One thing is true, they are involved in a terrorist outfit," he said.
"We have evidence to show that these people (the arrested men) established contacts in Mumbai and even came to Mumbai once," he said.
Asked if progress in the probe gave a clear picture about the conspiracy behind the attacks, Roy said, "We are deriving inferences from the evidence collected so far. Unless everything falls in place, we cannot come to a conclusion."
On the future of the probe, Roy said the ATS and Crime Branch and its teams have taken a "couple of steps in the correct direction" and hinted that another breakthrough was imminent.
Sources said the Crime Branch had detained four persons, including a software engineer and a doctor, in connection with the probe. The software engineer is suspected to have been detained from a southern city and was allegedly involved in assisting the perpetrators to exchange emails and other communications, sources said.
"We are waiting for the detention of one more youth who was involved in the blasts. After that we will consider whether to arrest the detained persons," a Crime Branch source said.
Some 200 people were killed and over 700 injured in seven blasts that rocked commuter trains here on July 11.
RDX explosives, ammonium nitrate and fuel oil was used in the bombs that were triggered by a timer detonator, forensic tests have revealed.