A Moss Beach man working as a contractor for the U.S. Army in Iraq has mysteriously disappeared while driving along an isolated road north of the country's violence-plagued Sunni Triangle.

Fears are growing that Kirk von Ackermann, 37, might have been abducted or killed after his car was found abandoned between the cities of Tikrit and Kirkuk. Found inside the vehicle were his satellite phone, a laptop computer and a briefcase containing around $40,000, suggesting that he had not been the victim of a robbery. There was no sign of a struggle at the scene.

Since his disappearance on Oct. 9, the Army has conducted an "aggressive" investigation aided by Iraqi police, said Chris Grey, spokesman for the Army's Criminal Investigation Command, based in Virginia. But so far they are baffled.

Initially it was thought that von Ackermann might have been kidnapped for ransom, but neither the authorities nor the company he worked for have been contacted by anyone claiming to hold him. His employer is Ultra Services, a company based in Istanbul that furnishes supplies and logistics help for U.S. Army bases in Iraq.

"It is a real mystery,'' one source close to the investigation said. "Kirk was on a day trip from Kirkuk to Tikrit that day and was coming back when he rang one of the company's Iraqi employees around 3 p.m. to say he had a flat tire and couldn't get it fixed with the jack he had. He was stopped right on top of a road that runs over a small range of hills ... at the time.

"The employee took about 45 minutes to get to him, and when he got there, Kirk had just vanished into the desert. There was no blood on the road or sign of a fight, no bullet cases fired anywhere, nothing. It was as if he had been abducted by aliens."

Friends and relatives at von Ackermann's home in Moss Beach declined to comment. Neighbors said they knew little about the missing man except that he was an avid cyclist who doted on his three young children and often walked an Irish setter.

"That's so sad," neighbor Michelle Harris told The Chronicle. "He has two young girls and a boy. They're the best parents I've ever met, and their kids are great. They're the epitome of the perfect family."

Ultra Services declined to comment on the disappearance.

Von Ackermann was said to be a former U.S. Air Force captain. A Web site for Impact Intelligence, LLC, lists him as a former employee and says he had been a member of a Department of Defense group that provided intelligence on terrorism, espionage, information warfare and other threats. It also says he has served as deputy director of intelligence for NATO operations in Bosnia. The information on the site could not be independently confirmed.

The case is thought to be the first disappearance involving a private contractor in Iraq. John Pike, an expert on defense and intelligence policy and director of GlobalSecurity.org, said the U.S. military routinely hired private-sector contractors to help with any task not directly related to warfare -- especially now that it is settling in for a long stay in Iraq.

Von Ackermann came to Iraq in late August to work as one of Ultra Services' contract managers. His work regularly involved driving between U.S. Army bases in and around Tikrit, Saddam Hussein's hometown, where Western civilians are rarely seen.

Von Ackermann was said to be well aware of the risks and was licensed to carry a pistol, which he always did. "The pistol wasn't in the car when it was found, and that suggests he had it on him at the time,'' said the source. "But he would have almost certainly shot at anybody who attacked him."

Investigators are puzzled about why von Ackermann was driving alone that day rather than taking an Iraqi colleague as he normally did, the source said.

The matter is being investigated by members of the Criminal Investigation Division of the U.S. Army's Fourth Infantry Division, which is based in Tikrit.

They have taken the abandoned car away for forensic examination and have interviewed both Iraqi and American employees of Ultra Services.

They have also conducted extensive ground searches of the area where the car was found but are reported to have turned up nothing. The area is extremely remote, with no obvious towns, villages or other spots nearby where von Ackermann might have sought help.

In Baghdad, the U.S. consul's office confirmed that they had been notified of his disappearance but referred all inquiries to the State Department in Washington. A department spokesman said: "There is an investigation ongoing ... but I don't think it has been categorized. The area is under the jurisdiction of the U.S. military."

With U.S. troops facing daily attacks in the Tikrit area, conducting an intensive search for von Ackermann would most likely be difficult. But even so, concerns are growing that not enough effort is being made by the U.S. authorities or Iraqi police.

At a U.S. Army checkpoint a few miles along the road from where von Ackermann disappeared, soldiers were issued with a photocopy of his photo ID several weeks ago. But during troop rotations, no information was passed on about the case, leaving the incoming troops unaware of who he was or why they even had his photo.

In the town of Baiji, where his disappearance was originally reported, the main police station had only passing knowledge of the situation. Col. Ismael Abdullah Jassim, the commander who led searches in the days immediately after the disappearance, left his post last month and did not brief his replacement on the details.

Lt. Muhamad Abdullah Jassim, one of Col. Jassim's deputies, said: "We took one of Mr. von Ackermann's colleagues out on a patrol to search for him and gave copies of photos of Mr. von Ackermann to local tribal leaders. Then we went out again just on our own. So far, we have heard nothing."