Police in Geneva have launched a series of controls around the city's airport after receiving information about a possible threat.
Preventive security measures are underway around the airport, the police said on their Facebook page, and will continue for an indefinite period.
Airport officials said the alert had been triggered after they had received an anonymous call.
Later, Geneva police said they received information from their French counterparts that led to a heightening of security at Geneva's Cointrin airport that straddles the border.
"The investigation will determine the facts, but it's not in our hands ... The French investigators will keep us informed," Geneva police spokesman Guillaume Gentil told Reuters. "The situation at the airport is calm."
Police also warned passengers of delays.