Union Home Secretary R K Singh said investigations into the serial blasts in the metropolis was going on and several people were being questioned based on their "previous known linkages".
"This investigation is on. We have identified the scooter in which one of the bombs was planted," he told reporters on the sidelines of a function here.
Asked whether there was any cross-border links to the Wednesday's blasts, the Home Secretary said: "We have an email which originated elsewhere. It is being followed up".
Singh said the CCTV footages of the three blast sites were being scrutinised by the investigators and they were going through the 11 CDs made from the footages.
"Now, we have all the people and the faces appeared. They have to be recognised by local people to see whether they are locals or outsiders. That process is on. There are 11 CDs which have been gone through. It is a voluminous work," he said.
The Home Secretary said people not recognised by the locals have been put through a data base and they were being verified.
"Suspicious people are being verified. Various people with previous known linkages are being questioned based on our previous data bases. This investigation is on," he said.
Asked whether the investigators were working on any definite lead, Singh said "we have not yet zeroed in on".