The U.S. military has opened a preliminary investigation into additional allegations of detainee abuse in Iraq.

In California Saturday, a military spokesman said the U.S. Navy launched the probe after being given photographs of Iraqi detainees allegedly being abused by Navy special forces in May 2003, months before the Abu Ghraib prison scandal.

The Associated Press news agency says one of its reporters found the photographs posted on the Internet, and turned more than a dozen over to Navy officials on Friday.

Also Saturday, pre-trial hearings for two soldiers accused of abusing prisoners at Baghdad's Abu Ghraib prison in late 2003 got under way on a military base in Texas.