British counter terrorism detectives are liaising with authorities in the United States amid reports of suspicious packages on cargo flights.
Officials are investigating reports of several packages on aircraft in the US cities of Philadelphia and Newark, New Jersey.
In Britain, parts of East Midlands Airport were closed earlier on Friday following the discovery of a suspicious package.
Police called to a freight distribution building and a number of offices at the Donington site are examining a suspicious package.
Several aircraft in the US have been moved to a remote location so law enforcement officials can investigate.
A Metropolitan Police spokesman said reports that a suspected bomb has been found on a flight in London are inaccurate.
Reports in the United States said a suspicious toner cartridge had been found on a cargo plane that landed in London on a flight from Yemen bound for Chicago. It has been claimed that tests found no traces of explosives.
Police evacuated a distribution centre at East Midlands Airport after a suspicious package was discovered in the early hours of Friday. Officers announced there was no threat shortly before 10am, but put cordons back up again at about 2pm.
Government officials in the United States said a suspicious package in Britain prompted the searches of cargo aircraft. It was claimed British workers found a toner cartridge which had been manipulated with wires attached to it, and a white powder. Tests for explosives proved negative but concerns about similar devices sparked the alert across the Atlantic.