A grass fire Wednesday tore through nearly 240 acres of the Carlos Avery State Wildlife Management Area in Anoka County.

The blaze started around 2:10 p.m. on 205th Avenue NE, just west of Wyoming, Minn. Two FireBoss planes from the Department of Natural Resources (DNR) helped fight the flames — first by laying down a fire retardant and later by dropping water scooped from a nearby lake.

The planes, which are updated models of the department's old fire-suppressing aircrafts, are working to control wildfires across Minnesota after a drought hit much of the state.

It remains unclear what caused the fire, but DNR officials don't believe it was driven by high winds like grass fires last week, as wind speeds were only 6 miles per hour in the area Wednesday.

Firefighters had the blaze under control by 4:30 p.m. and were working to put it completely out, said Lisa Wagner of the DNR's forestry division.

No injuries were reported or structures threatened as the flames spread throughout the park, which is a popular site for bird watching and hunting.

Previous fires in the area have caused significantly more damage, Wagner said, but this one was confined to the surface level and didn't seem to penetrate the flammable peat soil. Officials will check the site daily to make sure it doesn't flare up again.

Carlos Avery spans about 23,000 acres — 4,500 of which are posted as wildlife sanctuary and closed to trespassing. It consists of about two-thirds wetland, one-third upland and is managed primarily for deer, waterfowl and turkeys.