Hassoun, a 24-year-old Muslim with dual Lebanese and American citizenship, failed to return to the Marine base at Camp Lejeune, N.C., on Tuesday following an authorized holiday.

The Naval Criminal Investigative Service was investigating, but a spokeswoman said she could not comment on details of the case.

Hassoun's Marine Corps-appointed lawyer said there were no indications before the holiday that Hassoun would not return to attend his pretrial hearing next week.

“Corporal Hassoun was looking forward to having these charges adjudicated and seeing what evidence the government believed it had against him,” Maj. Phil Stackhouse said. "There's nothing to indicate to the contrary.”

Hassoun's family members in Lebanon and Utah had no insight into his disappearance. An agitated relative answering the phone at Hassoun's family residence in Tripoli, Lebanon, said everything they know has come from news reports.

"He was in the United States. That's all we know," the unidentified man said before hanging up. "I don't know what happened. I don't know what to think."

Hassoun's family in West Jordan could not be reached Thursday.

Several broadcast news reports said Hassoun had been tracked back to Lebanon. A security official, speaking to The Associated Press on condition of anonymity, said Hassoun was banned from entering Lebanon after he left the country in July.

Hassoun disappeared from the military base near Fallujah, Iraq, on June 20, and was initially believed to have deserted until an insurgent group released video of Hassoun blindfolded with a sword held above his head. Later rumored to be murdered by the group, Hassoun appeared in Lebanon, some 500 miles away, on July 8.

Hassoun insisted he had been kidnapped, but the Marine Corps charged him with desertion.

Retired Brig. Gen. David Brahms, a former staff judge advocate to the Marine Corps, said the pretrial hearing can't continue in Hassoun's absence, but the corps may use his disappearance as further proof of his guilt and may file additional charges. “My sense is they will not treat him kindly and may consider putting him in the brig as a way of keeping him around,” he said.

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Derek P. Jensen contributed to this report.