Four Metropolitan Police officers from the Royalty Protection unit are being investigated over an allegation of weapons property being mishandled.
The Met said in a statement: "Four officers, three sergeants and one PC, are the subject of the Directorate of Professional Standards investigations."
They added: "Officers from the Directorate or Professional Standards are investigating an allegation of mishandling of property from the weapons disposal bin by SO14 officers."
SO14 is the branch of the Met responsible for safeguarding members of the royal family and their residences including Buckingham Palace.
The bin in relation to this investigation was reportedly located at Buckingham Palace, although a Met spokesman said he could not confirm this.
None of the officers being investigated was arrested or suspended, a Met spokesman said.