Armed police are protecting the 12-year-old heir to the Belgian throne after an anonymous neo-Nazi threat.
A letter sent to La Derniere Heure newspaper threatened that its sender would abduct Crown Princess Elisabeth, in anger at high levels of immigration.
According to the Daily Telegraph, the letter was written in German, and read: "I'm going to abduct Princess Elisabeth. This is no joke."
Three armed police teams were dispatched to patrol the Princess's school.
DNA tests yielded no clues to the sender's identity. The newspaper didn't publish the full threat, which it described as a "sickening, racist and neo-Nazi" rant.
The newspaper said: "He expresses his disgust in terms that we prefer not to reproduce. Maghrebis, Turks and Muslims are covered by the letter."
Alain Lefevre, the director of Belgium's anti-terrorist unit, said: "The investigation has taken different directions but I obviously cannot reveal those.
"We will naturally take precautions as required. The case is now in the hands of a criminal prosecutor and forensic investigators are hard at work."