LONDON (AP) — London police are urgently investigating how armed protection officers guarding Mayor Sadiq Khan left a bag of guns outside his home.

The Metropolitan Police said in a statement late Friday that five officers had been removed from front-line duties while inquiries were being carried out.

The weapons cache, which according to The Sun newspaper included an MP5 semiautomatic Heckler & Koch carbine, a Glock pistol, Taser and ammunition, were found in south London Tuesday by a couple, who then informed the Metropolitan Police.

Scaffolder Jordan Griffiths told the newspaper that his girlfriend found the bag by the curbside and said that he was in “shock” after discovering what was inside.

“I could not believe my eyes and took some pictures as proof of what we had found,” he said. “I called the police and told them what I had found and within a few minutes they turned up to collect the guns.”

The police Directorate of Professional Standards is reviewing what happened and confirmed that five officers have been removed from front-line duties.

“We are urgently reviewing the circumstances of this incident and recognize the concern it may cause,” it said in a statement. “At this stage it is believed the bag was misplaced by on-duty officers a short time before the member of the public located it.”

A spokesperson for the mayor said the police “must now take all steps to ensure an incident like this never occurs again.”