Authorities said Friday they believe they found the shallow grave of a pregnant Marine in the back yard of a comrade she accused of rape, and a person close to the case said the suspect left a note insisting the woman had killed herself.

After some slight digging in a fire pit discovered in the yard of Marine Cpl. Cesar Armando Laurean, detectives found what "appeared to be burnt human remains," Onslow County District Attorney Dewey Hudson said Friday night.

"We think we have found what will (contain) the skeletal remains of Maria Lauterbach," Hudson said. Authorities placed a tarp and two white tents over the area and planned to begin slowly scraping the earth with garden tools Saturday morning.

Lance Cpl. Maria Frances Lauterbach, 20, vanished three weeks ago, days after she talked to military prosecutors about a rape case against Laurean, who remains at large. Authorities said Friday that information from another woman, a former Marine, left them certain that she is dead.

A source told The Associated Press that the witness is Laurean's wife. Before fleeing Friday, Laurean is said to have given his wife a note that said Lauterbach cut her own throat. Laurean is also said to have stated in the note that he had nothing to do with Lauterbach's suicide.

Lauterbach had claimed Laurean, her superior officer, sexually assaulted her, and she was worried that the investigation was going nowhere, according to court documents. She vanished last month before she was to testify in a military probe.

Brown said the officer had declined to meet with investigators, who no longer knew his whereabouts. Brown said he believes Laurean left town Friday. Paul Chiccarelli of the Naval Criminal Investigative Service said that Laurean was not considered a flight risk.

"They don't know where he is," Brown said of the suspect. "He's gone."

The court papers said the anticipated birth of the baby "might provide evidentiary credence to charges she lodged with military authorities that she was sexually assaulted by a senior military person."

Brown said a key witness in the case said Lauterbach was dead for some time.

She disappeared last month ahead of her expected testimony in a military investigation into her sexual assault. Court documents show the investigation went sour amid inconsistencies in the woman's story and allegations that she's bipolar and a compulsive liar. Search warrants show she was facing a possible discharge from the service.

Brown said the woman had bought a bus ticket to see her family in Dayton but never used it.

Lauterbach's mother reported her missing Dec. 19. Mary Lauterbach last spoke to her daughter Dec. 13. She said the family is concerned because it's out of character for her daughter not to stay in touch.

The Marine's cell phone was found near the main gate at Camp Lejeune the day after her mother reported her missing.