MENDON, N.Y. (NewsNation Now) — Three soldiers died Wednesday in a military helicopter crash in upstate New York.

Officials said three soldiers on board the New York Army National Guard UH-60 medical evacuation helicopter were killed in the crash while on a routine training mission.

It happened around 6:30 p.m. Wednesday in Mendon, a suburb of Rochester, NewsNation affiliate WROC reports. Witnesses said they saw the helicopter flying low to the ground before it crashed and caught fire in an open farm field.

Monroe County Sheriff Todd Baxter says emergency crews arriving on the scene saw the helicopter on fire in the field, and “went into life-saving mode.”

“This is a heavy heavy burden on all of us,” Baxter said. “We’re waiting for the National Guard for confirmation of who was on board and identification of our great soldiers.”

New York Governor Andrew Cuomo directed all flags on state buildings to be lowered to half staff Thursday, saying in part in a statement:

“I am devastated by the crash of a New York Army National Guard helicopter in the town of Mendon that killed three of New York’s bravest during a training mission,” Cuomo said. “National Guard members are our citizen soldiers who voluntarily serve and protect both here and abroad, and I extend prayers and condolences from all New Yorkers to the family, loved ones and fellow soldiers of these honorable heroes who we will never forget.”

According to preliminary reports from 911 calls, witnesses heard the engine sputtering as the helicopter was seen flying low to the ground before it crashed and burst into flames.

Officials believe three were killed in the crash but they are waiting for full confirmation from the National Guard on how many soldiers were on board. They continue searching for any possible survivors who may have been able to eject from the crash.

State police, the Sheriff’s Office, and several local fire departments all responded to the scene. The crash is under investigation.

Senator Chuck Schumer also released a statement Wednesday evening, saying:

“I am heartbroken by the news that three of New York’s brave Army National Guardsmen have been killed in a helicopter crash during a training mission. These National Guard members answered the call to help and serve their fellow New Yorkers and their country, and their sacrifices will never be forgotten. I send my deepest condolences to the loved ones of those soldiers killed, and the entire Monroe County community.”

This is a developing story; check back for updates. NewsNation affiliate WROC contributed to this report.