Members of the public are being warned not to approach missing man David Goodwin.
The 49-year-old last seen at the Jam Factory in Park End Street, Oxford, at about 10.30am yesterday.
The force launched an appeal in July after Mr Goodwin went missing. He was found the next day.
Police have described Mr Goodwin as white, very tanned, 5ft 10ins to 6ft, with light brown hair. One of his eyes is closed.
He was last seen wearing a tracksuit top, dark tracksuit bottoms and black leather shoes.
Anyone who sees Mr Goodwin is asked to call police on 101.