MINNEAPOLIS — Statewide fire restrictions took effect Friday, including bans on campfires, as an extended lack of rain, unusually warm temperatures and high winds combined to create explosive conditions across Minnesota.

The Department of Natural Resources limited open burning to special exceptions granted by county, state or federal agencies. Recreational or campfires were allowed only in designated fire receptacles designed for them at residences, campgrounds or resorts.

“The decision to restrict burning is not taken lightly,” said Larry Himanga, DNR wildfire prevention coordinator. “Conditions in the state have created a situation where an ignition source could result in extensive damage or injury.”

Four helicopters spent Friday dropping water on a wildfire that started Wednesday about 10 miles northwest of Greenbush in a remote part of far northwestern Minnesota, fire information officer Ron Sanow said. The Juneberry 3 fire has scorched more than 47 square miles, mostly grasslands, and come within a half-mile of the Canadian border. The soft, boggy soil has made it hard to bring in equipment.

“It’s an airshow at the moment. That’s not the way we like it,” Sanow said, but added that there were no injuries or damage to structures. The cause remains under investigation.

Firefighters who’ve been trying to suppress a fire in and near the Boundary Waters Canoe Area were trying to snuff out spots that were burning outside the lines they’d built around the Pagami Creek fire, which has been largely contained for several days. Lightning started the fire southeast of Ely on Aug. 18.

Officials are keeping an eye on a fire in a remote part of Voyageurs National Park that has burned about 100 acres of trees, brush and swamp. The fire started by lighting Aug. 28 is about two miles south of Namakan Lake and about 10 miles northwest of Crane Lake on the east side of Tooth Lake. Scott Bressler, the park’s fire management officer, said they’re letting it burn because it’s “out in the middle of nowhere” and doesn’t threaten people or property. He estimated it would take at least a half-day’s hike just to reach it.

Several smaller fires have been cropping up elsewhere around the state due to the dry conditions. Jean Goad, a spokeswoman with the Minnesota Interagency Fire Center, said tanker planes were sent to drop water on a 150-acre fire southeast of Red Lake on Thursday.

In southern Minnesota, five departments were called Friday afternoon to control a blaze that broke out in a cornfield seven miles east of Le Sueur.

The fire started near the Pioneer Power show grounds, where antique farm machinery is displayed in an annual show, Le Sueur County Director of Emergency Management Ann Traxler said. She said the fire did not damage the show grounds but did damage two small outbuildings at a farm.

“It was huge,” Traxler said of the blaze.

A separate fire in a wooded fire in Lexington also is under control, Traxler said.

A house near Lake Crystal was destroyed by a Thursday night fire that spread rapidly because of wind. The Free Press of Mankato reports the homeowners were awakened by smoke detectors and got out safely. The cause of that fire is under investigation.

When a cornfield fire broke out north of Austin in southeastern Minnesota on Thursday, farmers helped firefighters contain the burning brush by spreading a perimeter of manure around it, Mower County Sheriff Terese Amazi said. The fire started in a combine, but the machine was not damaged, she said. Nobody was injured, but two acres of corn were lost in the blaze.