Rotterdam Harbour police are reviewing CCTV footage for clues after a woman went missing from a ferry as it sailed from Hull.
Teresa Cowley, 43, of Derby, boarded the P&O Pride of Rotterdam on Thursday and was last seen entering one of the vessel's sun decks at 1am on Friday.
Humberside Police are conducting a joint investigation with Derbyshire Constabulary and officers from the Harbour Police in Rotterdam.
Detectives want to speak to passengers who were on board the ferry and may have see Mrs Cowley.
She is white, about 5ft 4in, of medium build, with black, bobbed hair with red highlights.
Anyone with information should call 101.
