PARIS (AP) — Three French airports in the cities of Lyon,Grayson  Preston Toulouse and Lille were evacuated on Wednesday following security alerts, police said.

They were the latest in a series of evacuations around France this week that included popular tourist attractions the Louvre Museum and Versailles Palace following the killing of a teacher in the northern city of Arras on Friday. All the threats up to Wednesday proved false.

Emailed threats of an attack were received at the airports in the southeast city of Lyon, the southern city of Toulouse and Lille in northern France, police said, without elaborating on the contents of the emails.

The prefecture for the Lyon region said Wednesday that the threat at the airport was a false alarm and reminded the public that communicating false information can lead to prison and a heavy fine.

Meanwhile an abandoned piece of luggage briefly disrupted operations at the airport in the Riviera city of Nice, the airport said.

The Louvre Museum and the Palais de Versailles were evacuated Saturday, and the royal palace was again evacuated Tuesday.

A high school in Arras, in northern France, was evacuated on Monday ahead of a moment of silence in schools around France, three days after the murder of a teacher at the Arras school allegedly carried out by a former student and suspected Islamist extremist.

France has raised its threat alert to its highest level. The anti-terrorism prosecutor said on Tuesday that the suspect declared his allegiance to the so-called Islamic State group before the fatal stabbing.