The helicopter went down during a routine training mission.

Three soldiers are dead after a military helicopter crashed in upstate New York Wednesday evening, the New York National Guard said.

The UH-60 medical evacuation helicopter, based at the Army Aviation Support Facility at Rochester International Airport, crashed in Mendon, New York, while on a routine training mission, according to the National Guard.

The helicopter went down at 6:32 p.m., the Monroe County Sheriff’s Office said.

Multiple fire departments responded to the crash, as well as state police and representatives of the U.S. military, the office said.

The road near the crash site remained closed.

The sheriff’s office did not state a cause for the crash.

The aircraft was assigned to C Company of the 1st Battalion, 171st General Support Aviation Battalion, according to the New York National Guard.

Flags on all state buildings will be lowered to half-staff on Thursday in honor of the soldiers, New York Gov. Andrew Cuomo said.

“National Guard members are our citizen soldiers who voluntarily serve and protect both here and aboard, 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,” Cuomo said in a statement.

ABC News’ Will Gretsky and Kelsey Walsh contributed to this report.

This is a developing story. Please check back for updates.