He wouldn't say where, but Adam McNab, the director of protective service for Fort Smith, N.W.T., said there is a specific area where the fire needs to be fully suppressed before residents can return to that community.

"It needs to be cold and wet along the outside of that area so it will not spread further," he said.

The incident command team has identified the area as a "trigger point of safe return," McNab said.

He added that firefighters have done "a lot of great work" in that trigger point area and that other parts of the fire have been reclassified as being held or under control.

Wednesday saw critical workers return to Fort Smith including, among others, RCMP, some health-care staff, grocery store staff and workers from the Northwest Territories Power Corporation.

McNab explained all the services are for direct support of the ongoing firefighting efforts in the community.

The town has also published a five-step re-entry plan; the return of critical staff is the first step with the second being the removal of sprinklers and other structure protection equipment.

"As soon as the trigger point is met, structure protection will be removed and essential services will be reestablished," reads the plan.

"Until these things have occurred the general population is not able to return."

In an update sent shortly before noon on Thursday, Wood Buffalo National Park said the northeastern perimeter of the fire that's stretching from Thebacha, down underneath Fort Smith and across to below Fort Fitzgerald has to be free of hotspots before a recommendation to return can be issued to the community.

"[It needs to be] extinguished far enough in that fire will not spread outside the current boundary," reads the update.

"Structure protection around communities will also need to be removed."

McNab said the fire is about 2.5 kilometres to the south of Fort Smith at its nearest point.

"There's much more heat over in the Thebacha area where there are a number of cabins and homes along the Salt River," he said.

"That area of concern is still a threat to the town of Fort Smith itself because it's so close to the highway corridor."

In the update, Wood Buffalo officials said crews were conducting heat scans to find hot spots and then extinguish them one at a time.

It added that crews were nearly done extinguishing hot spots on the northeastern edge of the fire closest to Fort Smith.

"Crews working in this area have been reporting two to three feet deep hot spots," the update reads.

"Putting out spots this deep requires a lot of effort, using different tools, equipment, bucket support from helicopters and lots of water."

With Yellowknifers allowed to return home on Wednesday, McNab said he was aware how difficult the ongoing evacuation for the community is for residents.

"I just ask for a little bit more patience," he said.

"I think that if we take those couple extra days to be absolutely sure we're safe, it's worth it because the last thing we want is to see anybody negatively impacted or hurt in the community if we return too soon."