During a training mission Thursday evening, two people aboard an Idaho Army National Guard helicopter were killed when the aircraft crashed.

Spokesman for the Idaho National Guard Col. Tim Marsano confirmed that the accident involving an Apache combat helicopter occurred around 7 p.m. local time, roughly two miles south of the Gowen Field at the National Guard base near Boise International Airport.

The victims were two male National Guard pilots.

"The men and women of the Idaho National Guard are united in grief at the loss of two of our brothers in arms, who gave their lives while training to defend our nation," Idaho National Guard Cmdr. Maj. Gen. Gary Sayler said in a statement. "Today, our thoughts and prayers are with their families."

The identities of the victims have not been released, and the cause of the crash is not yet known. Marsano said the Department of Defense will conduct an investigation into the helicopter crash.

Very few details regarding the situation leading up to the accident have been released. According to Fox News, Marsano said it is unclear whether any communication was heard from the pilots before the crash. It was also not immediately known if the pilots were heading to or returning from a mission.

He added that there was no fire at the crash site. Boise firefighters responded to the crash but soon turned the scene over to the National Guard, according to Fire Chief Dennis Doan.

Ada County sheriff's deputies blocked media access after securing the site.

This crash was the second involving U.S. military equipment Thursday. An Air Force F-16 fighter jet crashed into the Gulf of Mexico earlier in the day. Rescue crews spent much of the day searching for the pilot, the only person on board the plane. His body was later recovered in the Gulf.