Investigators on both sides of the Atlantic have begun examining how a Sudanese man was allegedly able to carry bullets on a flight from Washington to London.

The 45-year-old was arrested by detectives at Heathrow yesterday morning in a transit area, and was apparently carrying bullets in his coat.

He was initially arrested under the Firearms Act on suspicion of possessing ammunition, but has now been arrested under section 41 of the Terrorism Act 2000.

"The man will be interviewed by MPS Anti-Terrorist Branch officers," the Met police said.

In the US, the Transport Security Administration has begun examining records to check how the man was able to board the flight from Washington's Dulles Airport to London.