Mr Manson (28), whose parents John and Lynley live in Oamaru, was last seen leaving a bar in London St about midnight last Saturday. He has not been seen or heard from since.
Mr Manson suffers from epilepsy and fears are held for his safety. He was due to stay at an address in St Davids St, Lyttelton, but failed to arrive after leaving the Monster Bar.
Yesterday afternoon, Sergeant Phil Newton said no sightings of Mr Manson after he left the bar had been reported by the public.
Family and friends have been putting fliers in letter boxes and on vehicles around the area seeking information.