Police are today searching a "massive" area of the Tararua ranges after a man failed to return from a run yesterday.
Alastair Shelton, 33, had been running by himself around the Holdsworth Jumbo Circuit track, west of Masterton, yesterday morning but had not returned.
Police were contacted about 3pm yesterday.
Police were today widening their search, which Constable Pete Cunningham described as a "massive" area.
A helicopter was also being sent up to search the area from air.
Mr Shelton was described as "very experienced" and fit, with experience in orienteering.
He had run the Holdsworth Jumbo Circuit track in the past, Mr Cunningham said.
Police would like to hear from anyone that might have been tramping or walking in the area yesterday so they can begin to piece together a timeline.
Mr Shelton was wearing a singlet, black shorts, lyric tights, bright green running shoes and a small backpack.
Meanwhile, a helicopter will continue the search for missing tramper Alistair Levy in the Kahurangi National Park, near Nelson, today.
Poor weather conditions have been hampering search efforts for the 54-year-old, but a police spokesman said a helicopter was being sent back up today to continue searching the area.
Mr Levy left Nelson last Saturday morning. He sent a text message on Sunday morning to say he had tramped to 1875m up Mt Owen and had not been head from since.
The Palmerston North man was due to pick up his bike from a cafe in Kohatu and cycle back to his car at the start of the track at Courthouse Flat, but never made it.
He has been described as an experienced tramper but had no emergency locator beacon on him.