A "chaff module" fell from the transport aircraft - based at RAF Mildenhall in Suffolk - as it circuited the coastline on Monday, the USAF said.

The device containing flares is used to deter radar-guided missiles.

The USAF appealed for help in tracing the item but urged the public to stay away from it and not to use mobile phones when close by.

"Officials urge anyone finding objects with government markings to please report the find to their local constabulary," said a spokesman.

"For safety reasons, do not handle the chaff module or attempt to move it."

According to the American Air Education and Training Command website, a chaff module comprises "aluminium shavings that create an aluminium cloud to deter radar-guided missiles".

It also contains "flares" that can be detonated to "give off 3,000 degrees of heat to mislead heat-seeking missiles", the website said.