British police chiefs travelled to Germany today to demand a criminal investigation into the disappearance of a young woman, who has been missing for nine months.

Senior detectives are visiting Aachen as they bid to persuade a state prosecutor to authorise a new search for missing 24-year-old Louise Kerton.

Her sister, Fran, a University of York lecturer, says her family believes Miss Kerton is dead, but is becoming increasingly frustrated at the German police force's refusal to treat her disappearance as anything other than a missing person case.

"In Germany, to get it made into a proper crime investigation you have to go through the prosecutor's office and they say there is no evidence of a crime at the moment," she said.

"The British police are going with a dossier of evidence saying there has been a crime and that this disappearance is out of character for Louise. Hopefully that will convince them to move the investigation forward."

Fran Kerton, who lives in Fulford, York, also travelled to Germany last year in an effort to uncover more details about her sister's disappearance herself.

Louise, from Broadstairs, Kent, was last seen at Aachen Station on July 30 last year.

Assistant Chief Constable of Kent Police, Mike Bowron, and the senior investigating officer in the case, Detective Chief Inspector Brian Roberts, will discuss the matter with German police chiefs, the state prosecutor and the British Consulate.