Four female roommates at North Dakota State University on their way back to school from the Twin Cities died Monday in a crash on Interstate 94 west of Alexandria.

They were among six people who died within hours of each other on western Minnesota roads made treacherous by heavy snow and fog.

Among the young women was Danielle Rae Renninger, 18, a 2011 graduate of Minnetonka High School who was a passenger in a car headed back to Fargo after coming home for the Presidents' Day weekend, said her mother, Michelle Renninger, of Excelsior.

"She was just a beautiful girl," Michelle said of her daughter, a business marketing major who had made the dean's list at NDSU and loved college life, including sharing a suite with four other girls, three of whom died with her in Monday's accident. "Now there is just one left in the suite," she said.

Michelle Renninger said she, along with Danielle's father, Michael, and her 13-year-old brother, Logan, were "devastated" by news of the terrible crash. "She was such a wonderful, beautiful daughter," she said.

Danielle was active in dance at Minnetonka High School and had many friends, both in high school and at college, her family said.

She and her three friends, all from Minnesota, died just after 3 p.m., when their westbound vehicle crossed a median on I-94, in Douglas County, and was broadsided by an eastbound SUV, according to the Minnesota State Patrol.

The SUV that struck the women's vehicle was then hit from behind by another eastbound car. Injured victims in those two cars were taken to a nearby hospital, said Patrol Sgt. Jesse Grabow.

In the second crash, about 30 minutes later, a motorist died on Hwy. 28 in Pope County, south of the first accident. A westbound driver spun out on ice into the path of a vehicle driven by a 53-year-old man from Glenwood, Minn. The Glenwood man's vehicle hit the first vehicle, which then slid into a ditch. The first driver was killed; the Glenwood man was not hurt. A third fatal crash, in Douglas County near Alexandria at about 6:15 p.m., killed one person and injured two.

"Any way you put this, it's a bad deal," Grabow said. "Fatals are never good, and when you get four people in one vehicle it just makes it that much worse."

State Patrol officials had not yet determined with absolute certainty late Monday whether wintry weather was a factor in the crash that killed Renninger and her friends, but heavy snow, fog, strong winds and temperatures hovering around freezing were making for treacherous driving at the time.

The eastbound lanes of I-94 were closed after that crash, with vehicles detoured at the Brandon exit.

Grabow said weather conditions remained unfavorable Monday night.

"I'd advise people to use caution while traveling," Grabow said. "This is a reminder that winter is still here and we need to slow down and pay attention."

Metro roads dangerous

The bad weather stormed into the Twin Cities overnight, coating the roads with snow and setting up a potentially treacherous morning commute.

Up to 3 inches of snow was expected by Tuesday.

"It's not going to be fun," state Department of Transportation spokesman Kent Barnard Monday night. "It's going to be a challenge. There's only so much we can do out there."

Morning commuters who haven't honed their snow driving skills during this mild, snow-drought winter, will have to be patient and give themselves extra time to get to work, Barnard said. It could be a little slick in the morning and it absolutely will be slow.

"We've been spoiled this year," Barnard said. "We just want to warn people to keep their cruise controls off if the roads are a little bit slippery, don't tailgate and stay off the phone."

MnDot crews hit the streets Monday evening as snow began to fall in the metro area and continued to work through the night.

"The only advantage we have right now is that we're past the middle of winter and pavement temperatures are warmer," Barnard said. That means snow doesn't freeze onto the roads as quickly, making it easier for crews to remove. Road salt also is much more effective with the warmer temperatures, he said.

A 3-inch snowfall would tie for the second-highest this winter in the Twin Cities. Through Sunday, the Twin Cities had received 15.3 inches for the season; 38.5 would be normal.

Despite the unseasonably warm winter, the Minneapolis Park and Recreation Board announced Monday that it will extend the season at four outdoor rinks -- Lake of the Isles, Bohanon Park, McRae Park and Van Cleve Park -- until March 4.

Ice usually isn't maintained after Presidents' Day, and the city's other 43 rinks closed by Monday. But the agency will try to add about two more weeks to a season disrupted by frequent thaws and rink closings, said Park Board spokeswoman Dawn Sommers.