MARTY, Minn. – Three National Guard soldiers died Thursday afternoon when their helicopter crashed into a Stearns County farm field during a routine maintenance flight.

The soldiers paid the ultimate price, said a somber Gov. Tim Walz as he announced their deaths Thursday night during a news conference held near the crash site.

"My heart breaks for all the families, the friends and fellow soldiers," said Walz, who has a long personal history with the National Guard, having served for 24 years. "The coming days will be dark and difficult."

Investigators from Fort Rucker in Alabama are headed to Minnesota to help determine the cause of the crash, which occurred in a line of trees far from any homes.

National Guard officials said the names of the those who died will be released after their next of kin are notified.

"Our Minnesota National Guard family is devastated by the deaths of these soldiers," said Maj. Gen. Jon Jensen, adjutant general of the Minnesota National Guard. "Our priority right now is ensuring that our families are taken care of."

The UH-60 Black Hawk disappeared just after 2 p.m. after taking off from the Army Aviation Flight Facility near the St. Cloud airport.

According to emergency dispatch audio from Stearns County, nine minutes after takeoff, the helicopter's crew sent a mayday alert. The crash happened at 2:15 p.m., Chief Deputy Dan Miller said.

Several public safety agencies soon converged on the area in an intensive search for the Black Hawk and its crew.

Sherburne and Wright County deputies were the first to swarm to the area for the search. National Guard personnel, a Minnesota State Patrol helicopter equipped with thermal imaging cameras and the Minnesota Aviation Rescue Team, which includes St. Paul firefighters, soon joined the hunt.

As dusk fell, a State Patrol helicopter spotted the wreckage on the wooded edge of a field south of Cold Spring and about 16 miles southwest of St. Cloud.

Footage of the crash site showed extensive wreckage, and air ambulances were called off shortly after it was found.

At least two people saw the helicopter go down, according to the emergency dispatch audio, which also said there was no tracking beacon aboard the aircraft. No fire or smoke was seen.

The witnesses reported that "it went down hard," one dispatcher said.

Searchers estimated that the helicopter would have traveled 6 to 10 miles in the minutes since leaving the airport.

Dave Tannehill was the first in flight to help search for the missing copter. A flight instructor in St. Cloud since 2004, Tannehill said he brought a couple of other people with him for extra sets of eyes to help look.

"We were hoping to find a helicopter sitting in the middle of a field with a couple guys standing next to it looking for a ride. But not lucky enough to find that," he said.

Tannehill took off about 3 p.m. and was in the air for about an hour and a half. He circled the vicinity of the crash along with a military plane and police aircraft.

"It was bad news for everyone, and it was a quiet flight back," Tannehill said.

As news of the crash spread, Walz postponed a tree-lighting ceremony that had been scheduled for Thursday afternoon at the governor's residence in St. Paul and headed to the crash site.

He requested privacy for the victims' grieving families and friends and asked Minnesotans for their thoughts and prayers for those who died and those who knew them.

"They weren't just fellow soldiers," Walz said. "They were friends."

The governor and National Guard officials offered few details at Thursday night's news conference at the Holy Cross Catholic school in Marty.

Volunteers at the school prepared coffee, hot chocolate and snacks for law enforcement officials working at the nearby crash site.

Condolences streamed in across social media and from many political leaders, including Minnesota Rep. Bob Dettmer, R-Forest Lake, a 25-year Army Reserve veteran.

"We are heartbroken and devastated by the loss of three heroic Minnesotans," Dettmer said. "We also are tremendously grateful for our first responders who rushed to the crash site from the region and other parts of the state."

Said Minnesota Senate Majority Leader Paul Gazelka: "All Minnesotans are united in grief for our National Guard members who perished today. Today's accident reminds us of the dangerous job we ask them to do on a daily basis. No matter where they die, they are all heroes."

U.S. Sen. Amy Klobuchar also paid tribute to the soldiers. "Their service to our state and our nation will never be forgotten," she said in a written statement.

Staff writer Liz Sawyer contributed to this report.