Assistant Chief Constable Peter Lawson died at his home address on Sunday Morning.
Lancashire Police have confirmed his death, at this time, is believed to be medical related and has been referred to the coroner.
In a statement, Chief Constable Chris Rowley of Lancashire Constabulary said: "This is incredibly sad and tragic news. My thoughts and prayers are with all of Pete's family and friends at this difficult time.
"Pete's death will come as a shock to the entire force and the wider police family across the county. He was an outstanding officer who served the communities of Lancashire with pride. He was also highly respected and admired by all who knew him and worked with him.
"Out depest condolences go out to his family and we will support them as much as we can.
"We will offer support to our staff and those who worked with Pete, as we morn his loss".
ACC Peter Lawson worked on high profile cases, more recently the disappearance of Nicola Bulley, where he appeared at press conferences.
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