The bomb was recovered by the police near a tank at Thiruvathavur.
Reports reveal that the tiffin bomb was kept at Melur in the morning at around 7.00 am. The bus attendents threw it after no one claimed to come and collect it.
A local youth, who saw the lunch box being thrown out alerted the police.
The low intensity bomb which was timed to go off to go at 1.00 pm was however defused, said police. Investigations are one in the case.
Meanwhile, bullets were recovered from a Trichy bus, said sources.