HARRISBURG, Pa. (AP) — Investigators asked the public Thursday for tips in the stabbing death of a young Marine, found dead along the Pennsylvania Turnpike more than 40 years ago but only recently identified through DNA.

State police said the Marine had no identification on him when he was found Nov. 18, 1968, along the highway near Downingtown. He was identified in May as Cpl. Robert Daniel Corriveau of Lawrence, Mass. Police believe he was murdered.

Corriveau, 20, was found by a state trooper on patrol. He was in a seated position and had a stab wound to the heart.

Corriveau was wounded three times while serving in Vietnam in 1967. At the time of his death, he was receiving psychiatric treatment at Philadelphia Naval Hospital for what was described as a combat-related condition.

Investigators are asking for information that might help solve the case, including information on or from anyone who served with him in the military and people who were working or patients at the hospital in the months before he disappeared.

To provide information, call 610-268-5158 or email RA-1968MarineDeath(at)pa.gov.

(© Copyright 2012 The Associated Press. All Rights Reserved. This material may not be published, broadcast, rewritten or redistributed.)