Two Marine pilots were killed in a helicopter crash during a routine training exercise near Yuma, Arizona, the Marine Corps said Sunday.

The pilots, who weren't identified pending notification of their families, were in an AH-1Z Viper when the helicopter went down at about 8:45 p.m. Saturday, the service said.

No other details were immediately available as an investigation continues, said the Marines, adding the exercise was part of a weapons and tactics instructor course.