Dr. Charles Garrett, the Onslow County medical examiner, said the injury to Lauterbach was due to blunt force trauma.
The search for the suspect, Marine Cpl. Cesar Armando Laurean, entered its fourth day Tuesday with a $25,000 reward and a plan to post billboards of his picture nationwide.
There is concern that Laurean may be in Mexico and that he may be getting help from either inside the country or outside the country, reports CBS News correspondent Jeff Glor.
"The search for Laurean is Earthwide," Onslow County Sheriff Ed Brown said Monday. "It may be two days or two weeks, 10 days or 10 years, but you're never gone for good."
Lauterbach disappeared sometime after Dec. 14. The 20-year-old Dayton native had recently met with military prosecutors to talk about her April allegation that Laurean raped her.
Over the weekend, authorities recovered what they believe to be the burned remains of Lauterbach and her unborn child from a fire pit in Laurean's backyard in Jacksonville, N.C.
A neighbor says she saw something burning in the backyard and that Laurean asked to borrow a shovel, reports Glor.
On Saturday, authorities issued an arrest warrant on murder charges for Laurean, 21, of the Las Vegas area. They believe he fled Jacksonville before dawn on Friday, leaving behind a note in which he admitted to burying her body but said Lauterbach cut her own throat in a suicide.
Lauterbach's ATM card was found at a bus station in Durham, about 150 miles northwest of Jacksonville. Witnesses reported seeing his black four-door pickup truck in the Raleigh and Durham area, Brown said.
Other witnesses said they thought they saw him Saturday night at a .
Hundreds prayed for Lauterbach, the pregnant Marine hailed for her strength, vitality and service, even as law enforcement officials warned the man suspected in her killing that they would hunt him down.
Inside St. Christopher Catholic Church in Vandalia, Ohio, about 10 miles north of Dayton, hundreds of friends offered prayers Monday for Lauterbach.
"This evening, we are suffering," the Rev. Francis Keferl told a spillover crowd of more than 800 people.
A table outside the sanctuary held family photos of Lauterbach as a young girl huddled with siblings on a couch and blowing out birthday candles.
Lauterbach's mother, Mary, dabbed at her eyes during the 40-minute service. A congregant gave her a pink rose.
Mary Lauterbach has said the physical demands of the Marines appealed to her daughter, and that she liked boot camp. Her father, Victor Lauterbach, is an Air Force Reserve master sergeant, and the couple adopted Maria as a baby. They have four other children.
"She joined the Marine Corps for a big challenge," said Marine Staff Sgt. Sam Mao, a recruiter in Huber Heights, where she joined the Marines in 2006. "She was determined to succeed."
The FBI and United States Marshals are involved in the search for Laurean, who is expected to be charged with murder when he is arrested. The first billboards with Laurean's photo went up in Columbus, Ohio, and others are expected in Tampa, Fla., and Las Vegas.
Laurean's face is now featured front and center on the FBI's most-wanted Web page, reports Glor.
The military could seek charges at the same time as civilian authorities, said Scott Silliman, a former military lawyer who is now director of the Center on Law, Ethics and National Security at Duke University. But a joint prosecution is not recommended by the military's manual for courts-martial, Silliman said.
North Carolina is one of 15 states without a fetal homicide law, but Onslow County District Attorney Dewey Hudson said he has no plans to step aside in favor of a military prosecution.
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