Searchers stepped up their efforts Thursday to find a missing 20-year-old Toronto woman last seen in a rugged provincial park near Thunder Bay.

A missing poster for Christina Calayaca, 20, of Toronto, who has been reported missing in the Thunder Bay, Ont., area.
(Canadian Press)

Christina Calayaca has not been seen since Monday, when she went on an early-morning jog at the Rainbow Falls Provincial Park.

What she was doing at the park remains a mystery.

She had told family and friends that she planned to visit Montreal for a Christian retreat over the long weekend.

Provincial police are using sniffer dog teams and a helicopter. Authorities said they may try to use infrared heat-seeking equipment in their search later Thursday if Calayaca is not found.

Search officials have said her survival chances remain high despite not having any overnight camping gear.

But Calayaca's aunt, Karen Caguicla, said her niece would not be familiar with such rugged conditions.

"By no means is she an experienced outdoors person," Caguicla told CBC News Thursday. "If she has gone camping, it would be to a campground with everything there."

Fire department search and rescue teams from Terrace Bay, Schreiber and Marathon are helping with the search. Family members have also made the trip from the Toronto area to assist authorities.