US diplomat's wife leaves UK amid fatal crash investigation British police say the wife of an American diplomat who was a suspect in a fatal traffic accident has left the country

LONDON -- The wife of an American diplomat has left the country after reportedly becoming a suspect in a fatal traffic accident.

Police in Northamptonshire said Saturday they had been treating an unidentified 42-year-old woman as a suspect and that she had indicated she didn't plan to leave Britain.

The woman has been widely described across British media as the wife of a U.S. diplomat.

Police said they were preparing to arrest and formally interview the woman, who has not been officially named.

The accident on Aug. 27 killed 19-year-old Harry Dunn after his motorcycle collided with a car near RAF Croughton, a British military base near Oxford that's home to a signals intelligence station operated by the U.S. Air Force.

The U.S. Embassy in London offered its "deepest sympathies" to the family of the deceased and said it will continue to be in "close contact" with the appropriate British authorities.

"Any questions regarding a waiver of the immunity with regard to our diplomats and their family members overseas in a case like this receive intense attention at senior levels and are considered carefully given the global impact such decisions carry," a U.S. Embassy spokesperson said.

"Immunity is rarely waived."

British Foreign Secretary Dominic Raab said he called the U.S. Ambassador to express the U.K.'s disappointment.

Police said they were "now exploring all opportunities through diplomatic channels to ensure the investigation continues to progress."