(CNN) -- A slain Marine's fetus was not born alive, according to preliminary findings from a military autopsy, an Onslow County, North Carolina, district attorney said.
Lance Cpl. Maria Lauterbach's remains -- and those of her fetus -- were found in Laurean's back yard, police say.
"The initial opinion is that the fetus was not born alive," Dewey Hudson said.
Investigators say Marine Cpl. Cesar Laurean, 21, last month killed Lance Cpl. Maria Lauterbach Lauterbach, 20, and burned her body and buried it beneath a fire pit in his backyard.
She was eight months pregnant and had accused Laurean of raping her.
The military asked to conduct a second autopsy on Lauterbach following a state performed autopsy.
Lauterbach's family gave its approval for the Marine autopsy, which was completed Tuesday, Hudson said.
Hudson also said the military autopsy involved some procedures not done by the state, including reconstruction of Lauterbach's skull. The state autopsy indicated that Lauterbach died from a blow to the head, contradicting a note Laurean left for his wife saying that Lauterbach slit her own throat during an argument.
The military is performing further tests on a lung tissue sample to determine whether the fetus' lungs contained oxygen, he said.
If oxygen is found, it would mean the baby took a breath. In that case, Hudson said, Laurean could face a second murder charge. North Carolina does not allow murder charges for suspects accused of killing a fetus.
Additional tests are being conducted to determine if Laurean was the fetus' father, Hudson said.
Meanwhile, an 18-member North Carolina grand jury will convene Thursday morning at 9 a.m. to consider indicting Laurean on first-degree murder and other charges. Hudson would not specify what other charges are possible.
There will be an 11 a.m. news conference announcing the grand jury's decision.
Lauterbach was reported missing December 19, and the charred remains of her body were found January 11 after Laurean's wife gave police the note her husband had allegedly written. In the note, Laurean said he was frightened and buried the body in the back yard.
The Marine's note said Lauterbach died on December 15; authorities believe she was killed December 14.
Authorities believe Laurean fled to his native Mexico, where a cousin told CNN he saw Laurean near Guadalajara a week ago.
Hudson also confirmed earlier information from a law enforcement source on Tuesday that Laurean traveled by bus to Mexico. The source said he boarded a bus for Houston, Texas, on January 11, arriving the following afternoon.
In Houston, the source said, the Marine bought a bus ticket to San Luis Potosi, Mexico, probably arriving in Guadalajara on Sunday.
In the nearby town of Zapopan, Mexico, Laurean stopped at a liquor store owned by his cousin Juan Antonio Ramos Ramirez. Ramos told CNN Laurean said he was traveling "with some buddies for a few days."
"I did learn from federal authorities last week that Cesar Laurean left the U.S. and entered Mexico last Sunday morning on a bus," Hudson told CNN. "It doesn't surprise me a relative would have seen him -- assuming he is telling the truth -- because Laurean has family in Mexico."
Earlier this week, Hudson said that he had seen "strongly compelling evidence" from federal authorities that Laurean was in Mexico and that he had issued a provisional request to Mexican authorities through the U.S. State Department for the Marine's arrest.
If Mexican authorities arrest Laurean, Hudson would not be able to seek the death penalty because Mexico, like several other countries, will not extradite suspected killers if they face a possible death sentence. E-mail to a friend