Two crew members on board an Idaho National Guard helicopter were killed Thursday night when the aircraft crashed in Boise.

The two were on a night training mission, Col. Tim Marsano said. The helicopter went down about four miles south of the National Guard base at Gowen Field near Boise International Airport, the Idaho Statesman reported.

The Apache combat helicopter crashed at approximately 7 p.m. about two miles south of the National Guard base at Gowen Field near Boise International Airport, Marsano said. It wasn't immediately clear whether the pilots were heading to or returning from a mission, he said.

The Department of Defense will investigate the cause of the crash. According to Marsano, there was no fire involved in the crash.

"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," Maj. Gen. Gary Sayler, commander of the  Idaho National Guard, said in a statement.  "Today, our thoughts and prayers are with their families."

The Associated Press contributed to this report