Military officials are considering whether Marines who allegedly burned insurgents' corpses in Fallujah in 2004 did so for hygienic reasons.

If that's true, the alleged incident, which became public this week after the gossip news site TMZ published eight grisly photos, may not violate the Uniform Code of Military Justice, officials told Fox News.

Navy Rear Admiral John Kirby, however, said that even if burning the corpses was permissible, one of the photos, which depicts a grinning Marine kneeling over a skull, could raise separate problems.

"Aside from the burning, there were other images in that collection which are troubling for other reasons," Kirby told Fox News, adding that Defense Secretary Chuck Hagel is "deeply troubled" by the images.

WARNING: EXTREMELY GRAPHIC IMAGES

The Marine Corps, which has yet to authenticate the images, said an investigation needs to be completed before final judgment can be rendered and anyone can be held accountable.

TMZ, which made the photos public on Wednesday, said it has acquired 41 pictures, but has so far published only eight.

Some of the photos that were released show an unidentified Marine, his face blurred digitally, pouring gasoline on the dead bodies of slain Iraqi insurgents.

It was not clear if the faces of the Marine or Marines in the photos were blurred before or after TMZ received them.

Fallujah was the site of fierce fighting in 2004, with nearly 100 U.S. military personnel killed as the Iraqi city was seized from insurgents.

Earlier this month, Fallujah fell back into the hands of insurgents with the Al Qaeda-linked Islamic States of Iraq and Levant.

Fox News' Justin Fishel contributed to this report.