From a Reuters story:
A Dutch Catholic school called off a one-day trip to Paris for 400 students on Friday because of fears of an attack by Islamic militants in the French capital's metro, although French officials have cited no evidence of a specific threat.
The graduate students from the southern Dutch town of Etten-Leur had been set to leave on Friday but the school said in a statement that the trip had been canceled as a precaution after media reports about possible militant violence in France.
Iraqi Prime Minister Haidar al-Abadi said last month he had credible intelligence that networks affiliated with Islamic State insurgents were plotting to strike U.S. and French subway trains.
But senior U.S. officials and French security services said they had no evidence of a particular threat.
"The chance that something happens to our students is low, but we are ultimately responsible," Peter van Heusden, head of Catholic school KSE, said. "Concerns were expressed by parents and teachers about the terrorist threat."