BETHLEHEM, N.H. (AP) – Authorities on Monday abandoned the search for a 51-year-old Carroll hiker missing in the White Mountains wilderness since Jan 24.

Meantime, Bethlehem police were investigating his disappearance as a missing person case.

“We still have nothing positive or conclusive,” Fish and Game Lt. Todd Bogardus said. He added, “We have no reason to suspect foul play.”

He added that “if we get something that leads us in a positive direction, we will open up the search.”

Robert Sypek lives alone and has no family in the area, and no one had reported him missing, Bogardus said. Family members in Massachusetts confirmed they have not heard from Sypek during the past few weeks, Bogardus said.

Bogardus said his agency enlisted the help of a National Guard helicopter to search a 50-square-mile area from the air Monday for the self-employed computer engineer but ended the search when darkness began to fall.

The search began Thursday. Bogardus said no clues had turned up, other than tips from hikers who had gone into the wilderness with Sypek in the past.

Bogardus said temperatures dropped below zero and it was snowing and windy after Sypek left for a roughly 16-mile hike on popular trails, but he was known to leave standard routes to find new ways through the wilderness.

It snowed in the area again since Sypek left but Bogardus said the weekend’s unseasonably warm temperatures erased any trail he may have left.

“This is the proverbial needle in the haystack,” Bogardus said.

The search began when Sypek’s snow-covered car was found in Bethlehem, near Mount Garfield and the Gale River trailhead on Route 3. Bogardus said the car appeared to have been parked for about two weeks.

The search area was based on a note found in Sypek’s car outlining a route from the trailhead to the Gale Head Hut along the ridge of Mount Garfield, continuing to the Zealand Hut.