Two people on a high-speed train in southern France were questioned by armed police officers after railway officials raised concerns about suspicious behaviour, but the pair were not detained, a local administrator says.
The train's conductor had earlier announced on Friday that police had arrested the individuals on the train, which was travelling from Nice to Paris.
The passengers had refused to answer questions from train attendants or show their tickets.
They were switching seats and communicating between themselves with hand signals, an attendant in another section of the train told Reuters.
France is on the edge after a series of deadly Islamist militant attacks, the latest on Tuesday when two attackers killed a priest with a blade and wounded another in a church in northern France, before he was shot dead by police.
"Given the current situation, colleagues decided to ask the police to intervene," the controller said, requesting not to be identified.
"We have been instructed that if we have any doubt about anything, we should call it in," the controller said.
The train was delayed for nearly an hour as armed police searched the train's compartments, as obviously frightened passengers watched on, one of them crying.