Police and search and rescue experts say the information they have and conditions in Ontario's Algonquin Park give them hope they'll find two 16-year-olds who haven't been seen since Thursday.

Maya Mirota and Marta Malek, both from the Kitchener-Waterloo area, have been missing since the night of July 11 from the park, which is approximately 290 km west of Ottawa.

The two were last spotted on Western Uplands Trail near Rainbow Lake.

The camping group they were supposed to reunite with on Friday called Ontario Provincial Police when they didn't show up.

Nearly 100 police, park staff and trained volunteers continue to expand their ground search in the western area of the park, said OPP spokesperson Bill Dickson on CBC Radio's Ottawa Morning Monday, while a police helicopter and provincial government float plane look from the air.

"We're confident we will find these girls," he said, repeating they had a tent and some supplies with them when they were spotted on Western Uplands Trail near Rainbow Lake.

A longtime volunteer with the Ontario Search and Rescue Volunteer Association (OSARVA) said there are much worse times of year to get lost in the park.

"Hypothermia is not an issue; weather conditions have been good, relatively speaking … This is a search that should end well," said Fred Blackstein on Ottawa Morning.

"Water is the main issue and that's not an issue this time of year, food is not essential — psychologically it helps — the fact they had some supplies is excellent."

OPP also released new photos of the pair on Monday.

UPDATE: <a href="https://twitter.com/hashtag/OPP?src=hash&ref_src=twsrc%5Etfw">#OPP</a> continues the search for two missing 16 year old females, Maya MIROTA and Marta MALEK - last seen on Western Uplands Trail Algonquin Park on July 11th. Below are updated photos taken while in the park. If you have any information, please call 1-888-310-1122. ^kw <a href="https://t.co/BM6oGv1hRN">pic.twitter.com/BM6oGv1hRN</a> —@OPP_COMM_ER

Don't offer to help

Mirota is roughly 5 feet tall with a thin build and long auburn hair.

Malek is approximately 6 feet tall with shoulder-length, dirty blond hair, and wears glasses.

Anyone with information should call OPP at 1-888-310-1122.

OSARVA said it had two crews from the Ottawa area, one from near Brockville and one from Georgian Bay, helping with the search.

OPP are requesting people not come to the area to offer help because untrained searchers could themselves get lost or make it harder for their police dogs to pick up the girls' trail.

Both Dickson and Blackstein left open the possibility the girls may have made it out of the park. Dickson mentioned one possible sighting on Highway 60, the main road through the southern part of the park.