The UK Metropolitan Police have placed more than 20 officers on restricted duties over allegations that some fell asleep and left their posts unattended while guarding Windsor Castle, one of King Charles III’s official residences.

Twenty-three officers from the Royalty and Specialist Protection command, saddled with the responsibility of protecting the royal family, were served notices of misconduct, according to the London police.

While 21 were on restricted duties, the remaining two will not be deployed to royal residences, as the “urgent investigation” launched last month by the Directorate of Professional Standards (DPS) is still ongoing, the police said.

“The alleged behaviour falls below the high standards expected of officers, particularly in frontline protective roles,” a spokesperson for the force said.

The allegations were uncovered after a Sun newspaper report that some police officers had left their posts unattended and others had slept.

The police said investigations were ongoing at other British royal residences.

Windsor Castle, located in Berkshire, England, hosts official ceremonies and international state visits. U.S. President Donald Trump was hosted at the castle last year.