JACKSONVILLE, North Carolina (CNN) -- It's possible that a pregnant Marine missing since December 14 may have left willingly, perhaps after being upset by a phone call, documents released Thursday by Onslow County authorities show.

Lance Cpl. Maria Lauterbach last spoke to family members in the Dayton, Ohio, area on December 14.

Those records were bolstered by comments made by the county sheriff who pleaded for 20-year-old Lance Cpl. Maria Lauterbach, who is eight months pregnant, to come home.

The young woman's mother, Mary Lauterbach, told authorities that her daughter has a history of being a "compulsive liar," a police report states.

Mary Lauterbach described having a "firm conversation" with Maria Lauterbach about her unborn baby, telling her she should give the baby up for adoption because she is unable to care for it. Watch police face unanswered questions »

"Ms. Maria Lauterbach was telling Mary Lauterbach everything was fine, but Mary Lauterbach had a sense that the statements were not accurate," the report said.

Lauterbach last spoke to family members in the Dayton, Ohio, area on December 14. They reported her missing on December 19 after being unable to contact her.

Documents attached to a search warrant in the case cite the Marine's mother as saying Lauterbach had been the victim of a sexual assault by a superior officer.

Onslow County Sheriff Ed Brown said Thursday his office had not talked to the person accused in that case and referred any other comment to the Marine Corps. Officials at Camp Lejeune, North Carolina, where Lauterbach is based, have not commented on the assault allegations.

Earlier Thursday, Brown pleaded with Lauterbach to come forward and get help.

"Regardless of the circumstances, this has got to stop," Brown told reporters. "You can't run from those things in life."

While he would not say definitively that authorities believe Lauterbach is alive, Brown said he is leaning toward a positive outcome. "You pray that she's alive," he said.

Mary Lauterbach said her daughter claimed to have been sexually assaulted by a senior officer, but the military investigation had "gone sour," according to the Onslow County reports.

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When police consulted with the military on the allegations, the military reported that the case was open, but "it was difficult, due to inconsistencies provided by Maria Lauterbach, the reported victim."

Military investigators also "confirmed the history of compulsive lying," the report said, and added that Lauterbach was facing a possible discharge from the Marine Corps and was under personal and professional stress.

A Marine Corps Times story Thursday, citing unnamed sources, said Lauterbach may have fled her post after she withdrew the sexual assault allegations because she feared being charged with making a false statement. The newspaper said the allegations were lodged with Marine Corps officials last year and later withdrawn.

The Marine Corps is bringing Lauterbach's roommate, Sgt. Daniel Robert Durham, back to North Carolina from a training deployment in California to answer questions. Watch sheriff say why he'll talk with roommate »

The Onslow County report said that Durham told police that he had made his home available to Lauterbach "out of sympathy for her situation" and that the two had shared the home for only a short period of time.

Durham said he noticed nothing unusual in Lauterbach's behavior before she disappeared, but said "she had been upset by a phone call from her stepmother."

A few items of Lauterbach's were missing, he said -- her car, some cosmetics and clothing -- that led him to believe she may have left willingly. However, Durham told police that Lauterbach was confined to bed most of the time because of her pregnancy and that she "was in no shape for extended outings," according to the reports.

Brown told reporters Thursday that Durham is a close friend who may be the last person known to have talked with Lauterbach before her disappearance.

Mary Lauterbach told the Dayton Daily News on Wednesday that she last spoke to her daughter on December 14 in what she called "a very normal conversation."

The mother told CNN affiliate WDTN that later that day, she got a phone call from her daughter's roommate saying Maria had left their house.

After that, calls she made to her daughter's cell phone went unanswered, Mary Lauterbach told the Dayton newspaper.

Brown said Maria Lauterbach may have been due to give birth January 8. The police reports, however, said she was due on February 14, and did not show up for a prenatal medical appointment on December 28.

Lauterbach's cell phone was found on a roadside near Camp Lejeune on December 20. Her car was found Monday in the parking lot of a fast-food restaurant, Brown said, and had apparently been there since December 15. The car was processed, he said, but nothing of value was found.

Investigators have said that a withdrawal from Lauterbach's bank account was made on December 14 and there was "suspicious activity" on the account 10 days later. Police reports said Lauterbach's ATM card was used at a Marine Federal Credit Union by a man who attempted to cover the surveillance camera with a rag while he withdrew money from her account.

A search warrant released with the other documents Thursday seeks Western Union records, saying authorities have reason to believe Lauterbach may be receiving financial support through money transfers.

"Call mom!!! You know the number," says a Facebook page established to help find Lauterbach. "All of us love you and we miss you. Please come home!"

Lauterbach is a personnel clerk assigned to Combat Logistics Regiment 27, 2nd Marine Logistics Group, II Marine Expeditionary Force, the Marine Corps said. She joined the service on June 6, 2006. E-mail to a friend

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