Ontario Provincial Police have changed their approach in the search for a 20-year-old Toronto woman who went missing in a provincial park 16 days ago. Searchers are now looking for an "unresponsive person," having found no signs of anyone active in the bush. 

Christina Calayca was last seen on Aug. 6 when she went for a jog near the entrance of Rainbow Falls Provincial Park, on the north shore of Lake Superior about 200 kilometres east of Thunder Bay.

A poster portrays Christine Calayca, 20, of Toronto, who has been missing since Aug. 6. On Tuesday, police started a detailed search for an 'unresponsive person.'
(Canadian Press)

In the last 15 days, searchers have focused on covering the largest area possible in the shortest amount of time. With assistance from planes and dogs, police covered an eight-kilometre radius from the point where Calayca was last seen.

They have found a handful of clothing items and a footprint similar to that of the missing woman, but nothing has been directly linked to Calayca.

On Tuesday, the crew of 20 to 25 police officers changed their tactics, beginning a more detailed, grid-style ground search of the park, starting from the point where Calayca was last seen.

"Certainly we have significant concern for the survivability of Christina in this situation. There's been no sign of her active movement through the bush, and that means the searchers are now turning towards the possibility that we're dealing with someone who's non-responsive, so that could potentially include someone who has passed away," OPP Sgt. Deb Tully told CBC News.

Tully said that while the dogs and planes have been called off in the search, the effort is not being scaled back.

"We no longer require aviation support, when you're doing a search that's more detailed and more close to the ground," she explained. "The canine units are not going to be involved tomorrow, but they will certainly be brought in if we find a point of interest or feel that they're required."

The marine team will stay on and continue to search park waters. Tully said the OPP will take a day-by-day approach in determining how to proceed.

Still hope in case: searcher, father

Despite the change in tactics, rescue crews and the missing woman's family are maintaining hope that Calayca will be found alive.

"There's always hope," Tully said, noting that although night temperatures at the park are dropping to single digits, the search co-ordinator still thinks the weather is survivable.

The missing woman's father, Mario Calayca, said he believes his daughter is alive and well.

"Let's put it this way. The way I'm thinking, the way I believe, she just went for a walk, a long holiday, she just wanted to be alone at this time, and one of these days she's just going to turn up and let us know she's OK."

With files from the Canadian Press