FARGO, North Dakota (CNN) -- Fifteen helicopters from the U.S. Northern Command along with active-duty military personnel are being sent to Fargo, North Dakota, to assist the state as it prepares for record flooding, a U.S. military official told CNN.



Valley Water Rescue volunteers patrol the Fargo area in search of people who need help evacuating Friday.



The military personnel being sent to Fargo are from a "contingency response force" made up of active-duty troops, the official said.



Above-freezing temperatures, followed by heavy rains this week, caused the Red River to swell and surpass its 1897 record of 40.1 feet early Friday morning.



The swollen river threatened to rise further as the city's mayor vowed to "go down swinging.



"Right now, we think the river is beginning to crest," said Fargo Mayor Dennis Walaker. "As long as we stay under 42 feet, I think we got a chance; if we go over 42, there's going to be some more evacuations."



As of 8:15 p.m., the river churned at 40.78 feet, nearly 22 feet above flood stage and almost a foot above the previous record of 40.1 feet, set in 1897.  Watch Fargo's mayor explain why disaster could be averted »



Sandbagging operations, which have churned furiously throughout the week, continued Friday, drawing praise from local and state officials, including North Dakota Gov. John Hoeven.



"North Dakotans have come together in a big, big way. Our volunteers are doing a magnificent job building this flood protection and we want to say thank you to them," he said. "There's a sense of perseverance and resolve and determination."



Buses and evacuation staging areas have been staged west of Fargo, Hoeven said, and hundreds of people already have evacuated Fargo neighborhoods, hospitals and a nursing home.  Watch how volunteers are battling the rising water »



Fargo Deputy Mayor Tim Mahoney said authorities were evacuating the city's "vulnerable populations" and were asking for voluntary evacuations in sites near retaining dikes.



The National Weather Service predicted the river would reach 42 feet Saturday, and forecasts indicated it would remain there into next week. But the weather service warned the river might reach 43 feet -- the height to which most of the city's dikes have been raised -- if warmer temperatures expected in the middle of next week melt the record snowfall.  Watch Fargo residents fight back »



"What's going on here really is an inspiration for the country," said Sen. Kent Conrad, D-North Dakota. "The eyes of America are on Fargo, North Dakota, and they're getting a very good impression of what the people of North Dakota are like."



Authorities would not try to raise the city's dikes above 43 feet, Walaker said. Sandbags are used to bolster dikes in residential areas around the city, while the city dikes are reinforced with clay.



"We have most of the south side of Fargo, and along the river, good to 43, so we're not going to proceed with trying to get it to 44," he said at a news conference Friday morning. "Now is that a gamble? We don't think so."  See map of affected area »



National Weather Service spokesman Patrick Slattery in Kansas City, Missouri, said the river's level means uncertainty for officials and volunteers who are scrambling to mitigate the flooding in the area.



Emergency responders can extrapolate the effects of the rising river, he said, but they cannot know for sure how accurate the predictions are because they have never seen the river so high.



"At some point, especially when you're dealing with record levels, you reach a point when there's nothing else you can do," Slattery said. "Start alerting people to be ready to get out of there."



Lt. Gen. Russel Honore, who led the military response to hurricanes Katrina and Rita in 2007, warned that sandbags can only buy time.



"You cannot depend on a sandbag dike to save your life; you
When will the river reach 42 feet? What service commented on the river? Who praises volunteers for perseverance, resolve, and determination? Who was sent to help prepare? What neighborhood was evacuated? Who said the river will reach 42 feet on Saturday? Who did Govenor Hoeven praise?
Saturday, The National Weather North Dakota Gov. John Hoeven. Fifteen helicopters from the U.S. Northern Command along with active-duty Fargo The National Weather Service Our volunteers
question: When will the river reach 42 feet?, answer: Saturday, | question: What service commented on the river?, answer: The National Weather | question: Who praises volunteers for perseverance, resolve, and determination?, answer: North Dakota Gov. John Hoeven. | question: Who was sent to help prepare?, answer: Fifteen helicopters from the U.S. Northern Command along with active-duty | question: What neighborhood was evacuated?, answer: Fargo | question: Who said the river will reach 42 feet on Saturday?, answer: The National Weather Service | question: Who did Govenor Hoeven praise?, answer: Our volunteers