The wife of the suspected killer of a pregnant Marine knew she was dead a day before she went to police, according to affidavits obtained by local TV news stations in North Carolina.

Cpl. Cesar Armando Laurean and his wife, Christina, were driving to meet with an attorney on Jan. 10 when he told his wife that Lance Cpl. Maria Lauterbach was dead and he had buried her body out of fear, the affidavits show.

Laurean said Lauterbach, 20, slit her own throat with a knife during an argument on the evening of Dec. 15. He told his wife that Lauterbach, who was eight months pregnant, had come to him earlier that day to tell him she was leaving Jacksonville, N.C., and demand that he give her money. He took her to a bus station and helped her buy a ticket, his wife said in the affidavits.

Christina Laurean did not go to authorities with that information until Jan. 11, when her husband left home. She has not seen him since.

A search warrant has been issued for a cell phone belonging to Laurean, his wife, his mother and his sister, according to the affidavits.

WCNT-TV and WRAL-TV have obtained copies of the warrant and attached affidavits documenting conversations between 21-year-old Laurean — who is on the run and wanted in Lauterbach's murder — and his wife. Police said they do not believe Lauterbach took her own life.

Christina Laurean discovered Lauterbach was pregnant in July, but her husband said he was not the father of the baby, according to court documents. He also told his wife that he had not raped Lauterbach, as she claimed.

Christina Laurean has been cooperating in the investigation, police told FOX News.

Click here to see photos from the case.

Click here to view the FBI wanted poster for Cesar Armando Laurean.

As the manhunt for Laurean continued in the United States and Mexico, crime lab investigators were analyzing a weapon that might have been used to bludgeon the young woman to death.

A witness in the murder of Lauterbach turned the instrument over to police, who would not confirm local media reports that it was a crowbar.

"It was a person who had this item in their possession and did not realize its significance," Capt. Rick Sutherland of the Onslow County Sheriff's Office told FOX News on Thursday. "We have no reason to believe that they were involved in the homicide at all. ... We believe this item is consistent with the findings of the medical examiner."

Sutherland declined to say who gave police the item last weekend and what it was. Citing sources close to the investigation, The Jacksonville Daily News in North Carolina reported that the weapon undergoing testing at the lab was a crowbar.

An autopsy has determined that Lauterbach died of blunt force trauma to the head.

Meanwhile, the feverish search continued for Laurean, who authorities believe has fled to his birth country of Mexico.

The FBI in Charlotte, N.C., was spearheading the investigation and working with agents at the field office in Mexico City to try to track down Laurean, a naturalized American citizen.

"We suspect that he is in Mexico — we have not confirmed it, but we suspect it," Charlotte FBI Special Agent Newsom Summerlin told FOXNews.com.

It will ultimately be up to the Mexican government whether or not Laurean is extradited to the United States if he is caught. Mexico does not have the death penalty, and Laurean could face first-degree murder charges — which carry either a life in prison or death penalty sentence in the United States.

Detectives are working with authorities in Mexico to speed up the extradition process if the Mexican government does agree to send Laurean back.

"The FBI has well-established and pre-existing relationships at all levels of law enforcement in Mexico," said Summerlin. "We have had numerous successes in extraditing people back to the U.S. once local authorities have apprehended them. Among those who have been extradited are drug kingpins and accused murderers."

Mexico extradited 41 drug traffickers and dangerous criminals to the United States in 2005, 63 in 2006 and at least 80 in 2007.

The eight-months-pregnant Lauterbach disappeared in December, not long after she met with military prosecutors to talk about her April allegation that Laurean raped her. Laurean had threatened to flee to Mexico, where he still has some family, if a rape conviction against him appeared likely.

A wide-ranging manhunt for Laurean began last week, after authorities said he fled North Carolina and left a note in which he admitted burying Lauterbach's body but said she committed suicide. Investigators found Lauterbach's burned remains, and those of her child, in a fire pit in Laurean's backyard and concluded she did not kill herself.

Court documents filed this week by the FBI state that Laurean told members of his Marine Corps unit he would escape to Mexico if it appeared he would be found guilty of rape. Laurean's wife also told authorities she believed he would head to Mexico if he was in trouble. He was last spotted over the weekend at a bus station in Shreveport, La.

The court documents are included with an FBI criminal complaint charging Laurean with unlawful flight to avoid prosecution. He is also wanted in North Carolina on a state arrest warrant for murder.

Lauterbach died of "traumatic head injury due to blunt force trauma," according to autopsy results released Tuesday. But authorities said the exam failed to answer all the questions detectives have about Lauterbach's death, including whether she gave birth before her death and of the identity of the father.

Authorities believe Lauterbach was killed around Dec. 15. Marine officials said they attempted to find her after she failed to report to work on Dec. 17, but had evidence — including a note left for her roommate in which she wrote she was tired of the Marine Corps lifestyle — that led them to believe she left on her own.

FOX News' Catherine Donaldson-Evans, Marianne Silber and The Associated Press contributed to this report.