A Thomas Cook bureau de change cashier at Heathrow airport disappeared yesterday with £120,000 of foreign currency.
The man in his 20s who reportedly started work a few days earlier had keys to the safe and failed to return from his lunchbreak.
It was then that colleagues noticed the cash was missing.
Police could not find him at his home in west London and now an all-ports alert has been issued in case he tries to leave the country.
A Thomas Cook spokesman said: “We’re assisting police with their investigations and are unable to comment further.”