A Christchurch man is overdue from a solo tramping trip in the Mikonui River area, south of Ross near Hokitika.
Rex Leslie Taylor, 50, who is described as a fit and experienced tramper, left the Explorer Hut on 23 October and was expected out two days later.
Mr Taylor, who was travelling alone, was reported overdue on Tuesday and his car was located at the end of the Totara Valley Road.
Sergeant Sean Judd said searchers remained in the area overnight. Two dog teams and two teams on foot resumed the search on Wednesday morning.
A specialist white water team will join the search later.