The Royal Netherlands Marechaussee says they are still investigating the aircraft at Amsterdam Schiphol Airport.
German police have carried out searches in several apartments in Duisburg after nine officers were suspected of being members of extremist WhatsApp groups.
They will look into the prejudice allegedly committed against the general population, health care workers, civil servants and people sick or deceased.
Anti-corruption prosecutors are allegedly probing the alleged use by the former king, ex-Queen Sofia and some family members of credit cards linked to foreign accounts not in their names.
Minister of Defence Trine Bramsen says an investigation will look into the matter "with the utmost seriousness".