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The photos were sent to the Defense Department last week by the entertainment Web site TMZ, which said it had been told the pictures were taken in Fallujah, Iraq, in 2004 and the bodies were those of slain insurgents, a US defense official said.
The official said the investigation was complicated by the fact the face of at least one of the people depicted had been blurred to obscure his identity.
The metadata on the digital images received by the Pentagon did not include information about when the pictures were taken.
"We are currently investigating the veracity of the photographs, circumstances surrounding the photographs, and if possible, the identity of the service members involved," Marine Captain Richard Ulsh said in a statement.
"The findings from this investigation will determine whether we are able to move forward with any investigation into possible wrongdoing."
Some of the photos show an individual in what appears to be a Marine uniform dousing bodies in different locations in a compound with liquid from a military can typically used for carrying fuel.
Others show flaming bodies or charred remains. One shows a person in a Marine uniform carrying a rifle kneeling near a skull and looking at the camera. The person's face has been blurred to obscure his identity.
Defense officials said it was important to determine when and where the photographs were taken in order to understand whether the bodies were being burned with an intent to desecrate them or for some other reason, such as an attempt to deal with the problem of decaying bodies.
A defense official said none of the photos appeared to show violations of the laws of war but they could be violations of military orders governing the proper disposal of human remains and the taking of photographs with dead bodies.