DULUTH — Not even midway through winter, the number of snowmobile fatalities in Minnesota equals the total that died while riding all last winter.

Six people have died in snowmobile accidents in the past 10 days: Three were killed over the weekend, including a 12-year-old boy in southeastern Minnesota on Sunday, and a 55-year-old woman in northeastern Minnesota and a 64-year-old man in the western part of the state Saturday; two 21-year-olds died after a New Year's Day crash in Isanti County, and a 52-year-old man died while snowmobiling in Zimmerman on Dec. 31.

"One fatality is one too many," said Capt. Jon Paurus, the education enforcement and safety training manager for the Minnesota Department of Natural Resources, which keeps state records on snowmobile fatalities.

The especially snowy winter is getting more riders out on the state's 22,000 miles of groomed trails, he said, and "when we have good snowfall we have more people out enjoying the riding conditions, which tends to end up leading to more crashes with people on snowmobiles."

Blaze Himle, the 12-year-old who died Sunday, hit a tree while snowmobiling near Theilman about 10 miles southwest of Wabasha. Nancy Grieman, 55, of Albertville died when she apparently lost control while turning and struck a tree on Bearskin Trail 30 miles north of Hibbing. Scott Simdorn, 64, died when two snowmobiles and an ATV broke through the ice on Otter Tail Lake after dark over the weekend.

David Stewart of Zimmerman died New Year's Eve when his snowmobile hit a driveway approach, sending the machine airborne. In Isanti County, Faith Nelson and Hunter Melander, both of Cambridge, Minn., died after the snowmobile they were riding hit a tree. Officials have said speed and impairment possibly contributed to the accident.

The use of drugs and alcohol and excessive speed are things northeastern Minnesota snowmobile instructor Gary Mantay talks about in his youth certification classes.

"Speed has always been one of the biggest factors" in crashes, he said, with inexperienced drivers on machines too big or fast for their abilities.

The amount of snow the state has received in recent weeks has actually been limiting for many riders, Mantay said, with downed trees blocking trails and not-yet-frozen swampy fields.

The 12 snowmobiles available for rent at Nisswa Adventure Rentals in Nisswa, Minn., are regularly booked, and this winter is no exception, said manager Aspen Heilman. It is common, he said, for prospective renters to not know snowmobile certification is required to rent a machine.

Riders born before Dec. 31, 1976, don't need certification, which means a generation of riders isn't necessarily certified, said Jim Smeby, of the Inver Grove Heights Snowmobile Club.

"Snowmobiling has rules, just like cars," he said. "And a lot of middle-aged people have never been through a class."

Kids between 11 and 15 can take an online or in-person class, but both require a riding performance course. A certificate is valid at age 12. Adults born after 1976 are only required to take an online course. On average, about 10,000 adults and youth obtain certification annually, and the DNR said that, generally, that number has been on the rise.

Paurus said a leading cause of snowmobile fatalities each year is striking a fixed object, such as a tree, with about half involving drug or alcohol use. Riding at night in unfamiliar areas or when visibility is limited are also common factors, he said.

Mantay, who teaches with the Reservoir Riders Snowmobile Club in Fredenberg Township, north of Duluth, said snowmobiling is safest when you "slow down and stay to the right."

"Those are the things we are trying to teach the kids," he said, as he prepares them for riding. "You're having fun one minute and the next minute it can be a tragedy."

Grieman, the Albertville woman who died last weekend, was a single mother of three kids, ages 17, 19 and 20. A longtime restaurant server and a former flight attendant, she wasn't an avid snowmobiler, her family said, but she was adventurous, energetic and loved being outdoors.

"She lit up a room" and had a "one of a kind aura," her son Carter said. "She loved her kids so much and she would also talk about them and how proud she was. She gave everything she had to them."

Staff writer Paul Walsh contributed to this report.