(Adds details on helicopter)
WASHINGTON, March 31 (Reuters) - Two U.S. Marine pilots died when their helicopter crashed near Yuma, Arizona, during a routine training mission, the Pentagon said on Sunday.
The Marines were flying an AH-1Z Viper helicopter as part of a weapons and tactics instructor course when the crash occurred late on Saturday, the Pentagon said.
The cause of the crash is being investigated. The Pentagon said the identities of the pilots would not be released for 24 hours pending notification of next of kin.
The AH-1Z Viper, a twin-engine attack helicopter built by Textron Inc subsidiary Bell Helicopter, entered production in late 2010. The Marine Corps was to acquire a total of 189 of the aircraft, according to a March 7 news release. (Reporting by David Morgan; Editing by Dan Grebler and Daniel Wallis)