An autopsy revealed that a Peace Corps volunteer found buried in a shallow grave in a Philippine mountain village was killed by blows to the head, officials said Saturday.

Julia Campbell, 40, of Fairfax, Va., suffered "multiple blunt traumatic injuries of the head," police Chief Inspector Mamerto Bernabe, a pathologist who led the autopsy, told reporters at a suburban funeral parlor.

Crime laboratory head Chief Superintendent Arturo Cacdac said Campbell's remains were immediately turned over to the Peace Corps after the autopsy, which was observed by U.S. forensic experts.

Police are looking for a man who may have been involved in Campbell's death in the northern Philippines. Investigators said that a witness claimed he saw a man in the area of the shallow grave in Banaue township where Campbell's body was found on Wednesday, 10 days after she went missing.

Senior Superintendent Pedro Ganir, police chief of Ifugao province, which includes Banaue, said the man was the husband of a woman who sold a Coca-Cola to Campbell before she headed off on a hike in the area's famed mountainside rice terraces, a World Heritage site.

Ganir said investigators were looking into "robbery with homicide or rape with homicide."

Soldiers searching for Campbell — a freelance journalist who had reported for The New York Times and other media organizations — found one of her feet sticking out from the shallow grave in a dry mountain creek.

Campbell had been teaching English at the Divine Word College in Albay province's Legazpi city, southeast of Manila, since October 2006.