Acting on complaints from local residents, police visited Velayuthapuram and detained the 30 who had been brought by the PFI from various states for "teaching yoga, karate and other martial arts", District Superintendent of Police Kalirajan Maheskumar said.
He said said 11 of the detainees were from Bihar, eight from Assam, two from Karnataka and one from Kerala. Other eight were from Periyapattinam village in the district.
Police said PFI office-bearers had not sought permission for holding the drill in the sea coast.
They said rigorous drills had been given for some "unknown reasons" and those detained were being questioned.
The Special Branch police, who received information about the presence of strangers in the remote village from the locals, alerted the SP.