A U.S. Marine who allegedly deserted his unit after finishing boot camp at Parris Island months ago was back in Marine custody Wednesday after Millinocket police arrested him.

Peter Foster-Kinney, 22, of the Houlton area was returned on Tuesday afternoon to the Marine Corps from the Penobscot County Jail in Bangor, a Penobscot County Sheriff’s Department spokesman said.

If Foster-Kinney is found guilty of desertion, he could face several years in a military prison, although prosecutions and prison sentences are rare, according to published reports. Most cases end in discharge.

With more than 5,000 troops out of America’s 1.4 million active-duty troops and 865,000 part-timers having reportedly deserted since the war began in Iraq, desertion appears to be increasing, according to those reports.Marine spokesmen at Parris Island, S.C., and at the Marine Corps commandant’s office in Washington, D.C., could not immediately provide information Wednesday on why or exactly when Foster-Kinney left his unit.

Millinocket police Sgt. Aaron Brooker and Officer Ron McCarthy found Foster-Kinney almost by accident, McCarthy said. The officers went to a Bates Street residence in Millinocket on Monday afternoon on a report of an argument. There they found Foster-Kinney, who was dating a woman who lived there, McCarthy said.

“We talked to him, and because he was a face we didn’t recognize, we ran his name and date of birth, and that’s how we found out,” McCarthy said Wednesday.

Desertion charges in Maine are rare, McCarthy and Police Chief Donald Bolduc said.

“I’ve been doing this for six years, and we’ve only seen a handful of cases,” said McCarthy, who served in the Army as an infantryman and tank driver in Hawaii and at Fort Benning, Georgia, from 1989 to 1996. “All we do is pick them up and turn them over.”

Soldiers are usually classified as deserters when they have been absent without leave for 30 days and show no intention of returning, said Capt. Gabrielle Chapin, a media officer in the Division of Public Affairs Headquarters at U.S. Marine Corps headquarters in Washington, D.C.

Calculating the number of Marine deserters is complicated because the Marine Corps carries on its books those who have deserted in previous years, Chapin said. The Marines count 1,297 deserters in fiscal year 2004 and 1,159 in fiscal year 2003.

The number of deserters returned to the Marines annually was not available.

The number of Marine deserters peaked in fiscal year 2001 at 1,705. About 1,676 deserted in FY 2000, she said.

If Foster-Kinney completed boot camp, which runs 13 weeks, he would have been given 10 days leave before having to report to Camp Lejeune in North Carolina for Marine combat training, said Lt. Scott Miller, deputy public affairs officer at Parris Island.