The investigation into the slaying of federal prosecutor Jonathan Luna (search) is focusing on his personal life, and the information being dug up is totally "erroneous," Luna's father told Fox News on Sunday.

Luna's mother and father told Fox News in a phone interview Sunday that they are very upset with this new turn in the investigation into their son's murder, and that all the details about their son and sex Internet sites, financial problems and allusion to extra-marital affairs are absolutely "not true."

Investigators are looking into messages posted by a "Jonathan Luna" on a Web site where people advertise for female sex partners, according to a federal law enforcement official who spoke to The Associated Press on the condition of anonymity.

Whether or not it was the federal prosecutor who posted the ads is unknown -- Time magazine reported that there's a much younger man who is a convicted sex offender also named Jonathan Luna.

Luna also traveled several times in recent months to the area of Pennsylvania where his body was found, and authorities were not immediately aware of any work-related business that would have taken him to the region.

A credit card Luna held without his wife's knowledge is also being investigated.

Baltimore FBI spokesman Larry Foust (search) said Sunday that investigators were still trying to determine a motive for Luna's killing.

"This is a full-court press, but we just don't know. There's a lot of information and a lot of misinformation out there," Foust said. "We have people working nonstop, overturning every stone, going where the facts lead them."

While the federal law enforcement source told the AP that investigators had found nothing to indicate the killing was related to Luna's work, Luna's father and friends are convinced his death was tied to his career.

For years, Paul D. Luna (search), 83, had urged his son to return to private practice instead of prosecuting drug dealers and violent criminals. The assistant U.S. attorney had just worked out plea deals in one drug case late Wednesday, hours before he was found dead, stabbed 36 times and left face down in a Pennsylvania creek.

"I was warning him many times," Paul Luna told the AP on Sunday. "I'm very positive that this is for his work. I even told that to the FBI."

He said two FBI agents interviewed him for about three hours Saturday.

The same day, investigators were in Lancaster County, Pa., showing hotel owners pictures of the slain 38-year-old prosecutor. Hotel owners and managers said they were asked to review their guest registers for Wednesday and Thursday nights and asked if they had video security cameras.

Paul Luna said he told the FBI agents about a planned trip to New York after Thanksgiving, which was the last time he saw his son.

"I reminded him about taking me to New York. He says, 'Not this week, Dad. I'm sorry, because I have a case. I have to go to Pennsylvania,'" he recalled his son saying. Paul Luna said he didn't know what the case or trip was related to and that his son rarely told him details about his work.

He said investigators also asked him whether his son had any financial dealings with anyone and whether he was having financial problems.

"I don't think he was having problems because he was planning to go to the Philippines with me next month," said the father, who is from that country. "So if he has problems, why should he do that?"

Friends also said money was never a problem for Luna. Though he was a successful prosecutor and his wife is an obstetrician, they own modest family sedans.

They bought their Elkridge townhouse for $174,900 in 2000. They talked later about buying a bigger home but decided against it because they would rather spend the extra money on family vacations, said neighbor Dana Stango.

Paul Luna said he gave investigators names of his son's friends in New York, where his son had been an assistant district attorney in the late 1990s.

He also said he was asked about relationships his son may have had but said he had no knowledge of any possible extramarital affair. His son appeared to be happily married to his wife, Angela, he said.

"It looked like they were very much in love with each other," Paul Luna said. He said he saw the couple and their two young sons frequently.

Two of Luna's friends in New York also believe his death is connected to his job, though they said he never expressed fear of the people he was prosecuting.

"Those that he was putting away were more likely than personal acquaintances, I think, to take that kind of action," said Merlin Bass, a New York tax attorney who roomed with Luna during law school and remained close to him.

Reggie Shuford, another former University of North Carolina law school friend, said he was shocked when he heard investigators were probing Luna's personal life.

"It's absolutely amazing to me," Shuford said. "I cannot fathom that."

Bass and Shuford said FBI agents called them over the weekend to ask about their friend. Shuford said investigators told him his name was in Luna's Palm Pilot and was mentioned by Luna's father. In response to their questions, Shuford told them Luna didn't have a girlfriend or any money problems.

Paul Luna said he had not heard from investigators on Sunday, but planned to call them Monday to find out how much closer they were getting to "nail down this criminal who killed my son."

"He killed my son, but he also killed me," he said.

Fox News' Rebecca Gomez and The Associated Press contributed to this report.