The number plate of the bike has been traced to a retired telecom employee here, who said that he had sold the bike about four years ago, a police source said.
The two-wheeler with a Tamil Nadu registration number (TN 22 R 3769) belonged to KS Sankaranarayanan, a resident of Thillai Ganga Nagar in Chennai, they said.
"The bike was in my son's name. But we sold it about four years back, since my son left for the US", he told the police.
Sankaranarayanan, said he was shocked when police knocked his door and told him that the bike had been used in the Bangalore blast.
Police sources said that while they were tracking down the number plate of the bike, they were also inquiring whether a fake number plate was used.
Investigations are on with the state police coordinating with their counterparts in Karnataka and the National Investigation Agency, the sources said.
Terror struck Bangalore yesterday ahead of the upcoming Karnataka Assembly elections when a low-intensity bomb exploded near the bustling BJP city office in a busy residential area injuring at least 16 people, including 11 policemen.
The bomb, apparently strapped to the motorbike with a Tamil Nadu registration plate parked between a van and a car, went off around 10.30am about 100 metres diagonally opposite BJP office in Malleshwaram.