An unidentified person had handed over the bags to the shop owner asking him to take care of it for a few minutes, but did not return to collect them, they said.
The shop owner became suspicious and informed the police, who searched the bags and found that they contained the bombs, they said.
A search is on for the suspect, police said.
On June 3, an Improvised Explosive Device, packed in a tiffin box, exploded on Vaigai river banks here, setting ablaze a stationary lorry.