The U.S. Navy is investigating claims Marines killed up to 10 unarmed Iraqi captives during a battle in Fallujah in 2004.
Military officials say the criminal probe centers on several members of the Marine Corp's Kilo company. Different members of the company have also been accused of the deaths of 24 civilians in Haditha, Iraq in 2005.
The latest investigation began when former Marine Ryan Weemer asked during a polygraph test for a job with the U.S. Secret Service, if he had participated in a wrongful death.
The Secret Service reported the allegations to the Naval Criminal Investigation Service (NCIS).
An account of Weemer's story was published online at DefendOurMarines.com by Vietnam veteran Nat Helms who wrote a book on the Marine Corp's battle for Fallujah.
Some information for this report was provided by AP and Reuters.