The Gare du Nord train station in Paris reopened on Tuesday after a security alert, officials said.

Platforms were evacuated and the area cordoned off by heavily armed police late Monday evening, the BBC reported.

Paris police tweeted (in French) early Tuesday morning: “End of security checks. Gradual return to normalcy.”

No details have been given about the operation in one of Europe’s busiest transport hubs, but according to the French Le Parisien daily, the police were looking for three men described as “dangerous” to French security forces by a foreign country.

The daily said the operation focused on a train from Valenciennes in northern France.

The suspects were spotted in Bordeaux and Marseille, as well as in Paris.

Police had launched operations in each city, but could not capture them, the BBC quoted the daily as saying.

France has been on a high state of alert since the November 2015 attacks by the Islamic State militant group that killed 130 people.

The incident also comes a day after independent centrist Emmanuel Macron won the presidential election by defeating far-right National Front leader Marine Le Pen.