Though the Special Investigation Team probing into the blast at the District Collectorate on July 10 last year have almost zeroed in on the main suspect, the case is nowhere near closing.
The investigators have traced the suspect, believed to be having a direct link with Lashker-e-Taiba, to Oman.
But he could not be extradited as India does not have an extradition treaty with Oman.
A senior police official involved in the investigation said that the chances of bringing him over weigh mostly on the National Investigation Agency, by including him as a suspect in cases of terrorism already being probed.
This could be done as main suspects are linked to all activities.
A low intensity, high-decibel explosion was made on the fifth floor of the District Collectorate at Kakkanad on July, 2009, afternoon, inflicting a minor injury on an employee.
The attack was planned and executed with minimum persons, only two or three.
This makes it vital to get to the main suspect, as only he could lead to other suspects involved in the crime.
The intensity of the explosion was kept deliberately low as it was more of a sort of challenge to the law-keepers, announcing the presence of the group, police sources said.
The security at District Collectorate was stepped up, though not to fool-proof level, after the incident.