A man with a knife has been arrested by police at Paris’ Gare du Nord station, sending a brief ripple of concern over social media a day before the French presidential vote. No one was injured. A French police official told The Associated Press that a man carrying a knife walked into the station and was flagged to police, who arrested him immediately. Video online shows heavily armed police surrounding a prone man as travelers hurried past. The official spoke on condition of anonymity because she was not authorized to speak publicly. The Gare de Nord is one of the French capital’s top transit hubs, serving the city’s metro, suburban trains as well as intercity and high-speed trains like the Eurostar from London.