More than 2,000 high school students in northern France were evacuated Monday after an internet threat, authorities said, but a police search did not find evidence of danger.The threat was posted on Twitter by a young man who claimed to have placed radio-controlled bombs in hidden locations, broadcaster France Info reported.Shortly after the evacuation, authorities in the Oise prefecture said the national police had not found any suspicious articles on the grounds of the Mireille Grenet school, located nearly 100 kilometres north of Paris.Judicial police were investigating to find the author of the threat and uncover a potential motive.France has been in a state of emergency for two months since a series of terrorist attacks in Paris on November 13 left 130 people dead.A man wielding an axe was shot dead outside a Paris police station last week, the latest in a series of incidents that have set the country on edge and prompted a broad debate over security.