"Such things are taken seriously and we are probing about this letter," Tiruchirapalli Police Commissioner Shailesh Kumar Yadav told PTI adding a 24 x 7 Bomb Detection and Disposal Squad (BDDS) was always on duty in the temple premises.
"All the three entry-exit points to the temple are on guard on a permanent basis and all the visitors are thoroughly frisked," he said adding a similar letter was received sometime ago.
Another police official said the letter in Tamil was written by an unknown person.
"He has used a name which appears to be fictitious alongside the name of a video outlet that is functioning here. We are probing. We also want to see if this threat letter is used to settle personal scores," the official said.