Mayor Bill Enouy said fires can flare up at any moment, and a fly-over with infrared cameras on Thursday morning showed many lingering hot spots.
"It's like a forest that somebody painted black, so there's still lots of fuel out there for a fire if it stands up," he said.
Firefighters remain in place and while the winds are "terrible," they are blowing from the southwest which doesn't pose an immediate threat to the town of about 9,000.
"If it starts coming from the northwest it becomes a bigger problem because it starts blowing the front towards the community," Enouy said. "We're at the mercy of the gods."
There are currently 45 active forest fires in Ontario, with 43 of them in the northeast region.
Carin Glassford, a spokeswoman for the Ministry of Natural Resources, cautioned that the blaze burning northeast of Kirkland Lake is not yet classified as being extinguished entirely.
Fires can often look like they are out, but they can burn "quite deep" and wind can cause fuel to re-ignite, she said.
"If you were to fly over it, it's not like huge flames burning but that does not mean that the hazard is reduced or that we're out of a problem situation," she said Thursday in a phone interview from Sault Ste. Marie.
The "long, narrow" fire is about 2,700 hectares in size and is located five to 10 kilometres away from the city.
Warm, dry weather is expected for next few days and with increased winds, fire activity is expected to pick up, Glassford added.
"There's certainly an issue of smoke, potential of fire and residents in the community of Kirkland Lake are on standby in the event they need to evacuate," she said.
About 300 Kirkland Lake residents who live around lakes outside the town's urban area have already been evacuated. Some are staying with family or friends or in hotels.
Meanwhile, residents are being kept informed through local media including the town's website.
"The message is don't panic but be prepared," the mayor said.
Firefighters were busy at the scene Thursday, trying to get rid of piles of brush that could provide fuel. Helicopters were also helping to water down some areas.
Natural Resources has a team on the scene to assess the fire, as well as firefighting crews on the ground.
Waterbombers from Newfoundland and Manitoba have been assisting Ontario's firefighting efforts.
Another 80 fire rangers and a 20-person management team was expected to arrive Thursday from British Columbia and would be ready to deploy Saturday.
Premier Dalton McGuinty spoke to firefighters and emergency workers in Kirkland Lake Thursday, thanking them for their continued service.
"Our North is beautiful, but it can also be dangerous. The spring forest fires that have threatened northern towns are a fresh reminder of that," McGuinty said in a statement. "But Northerners are tough, resilient and determined — and I know they’ll get through these challenges, too."
In the Timmins area, about 140 kilometres northwest of Kirkland Lake, Natural Resources said there were concerns that shifting winds could cause a different fire there to begin spreading east.
The ministry said an emergency was declared at the Mattagami First Nation south of Timmins and 118 residents were evacuated to Kapuskasing.
Officials warned strong winds could cause significant smoke to enter the communities of Timmins and Gogama.
— By Linda Shearman in Toronto