Highly-placed sources said a proposal has been pending with the government for the last three months as the Indian High Commission in Colombo is yet to take permission from Sri Lankan government for allowing a NIA team to visit the island nation.
As per the Mutual Legal Assistance Treaty (MLAT) between the two countries signed in 2010, any requesting country can send its team to pursue and carry out further probe in that country.
The terror plot was unearthed by Malaysian Special task force which was investigating a routine human trafficking case. Immediately, Intelligence Bureau was informed who arrested one Sakir Hussain in Chennai.
Hussian, a Sri Lankan national, has since been convicted to five years imprisonment for being involved in the terror plan.
Besides probing the role of Siddiqui, NIA wanted to verify some of the phone numbers and also question people detained by the Lankan police in this connection.