A police protection officer travelling with the foreign secretary has been suspended from duties after leaving his gun on a plane.
The weapon was reportedly found by a cleaner on a plane at Heathrow Airport.
Dominic Raab had been on a visit to the US and the officer had been travelling with him.
A Met Police statement said: “We are aware of the incident on a flight into the UK on Friday, 18 September and we are taking this matter extremely seriously.
“The officer involved has since been removed from operational duties whilst an internal investigation into the circumstances is taking place.”
Dominic Raab travelled to Washington in an attempt to smooth the path for a UK-US trade deal
The Sun reported that police were called to the aircraft after the Glock 19 pistol was discovered in its holster on a seat.
A source told the newspaper the officer had taken off the firearm while sorting out passports and preparing to escort Mr Raab off the flight.
The United Airlines aircraft had been on an overnight flight from Washington DC before disembarking at Terminal 2.
In February this year, police investigated claims former prime minister David Cameron’s bodyguard left his gun in a plane toilet.