A veteran Boeing aerospace engineer from Orange County has been arrested by the FBI on a charge of possessing child pornography on home computers.

Keith Gartenlaub, 46, was arrested last week after an investigation that included monitoring authorized by the Foreign Intelligence Surveillance Court, according to his lawyer and court filings.

Gartenlaub lived in Irvine until his home was raided by the FBI in January and is now staying in Laguna Hills, the FBI said.

Gartenlaub’s lawyer said he apparently has been fired after more than 20 years with Boeing. A government court filing said he worked on “sensitive military matters.”

Gartenlaub could face nine to 11 years in prison if convicted, a prosecutor said. He’s scheduled to be arraigned Sept. 29.

An Aug. 27 complaint filed by the FBI doesn’t make clear why agents began investigating Gartenlaub, but it said a search of his home in January turned up three hard drives with videos of child pornography, including ones of girls who appeared to be 10-12 years old.

Agent Kenneth Cooper said in the complaint that Gartenlaub worked as an application administrator in a corporate information technology division. The way the illegal videos were saved showed Gartenlaub’s computer expertise, as he hid them in subfolders under layers of folders with innocuous-sounding names such as OrigData, tmp, Administrator and System, Cooper wrote.

The FBI complaint said Boeing had been monitoring Gartenlaub’s computer use and had records of him remotely logging into his home computer from work and looking through folders containing pornography, though not of children.

The case is being prosecuted by lawyers with the National Security Section of the U.S. Attorney’s Office in Los Angeles, and a court filing shows the government obtained unspecified evidence against Gartenlaub under the Foreign Intelligence Surveillance Act.

That law set up the Foreign Intelligence Surveillance Court, which hears classified evidence and issues secret warrants authorizing the FBI and National Security Agency to wiretap people and seize evidence for foreign intelligence purposes.

Gartenlaub’s lawyer, Mark Werksman, said he has been told the investigation began with FISA warrants, but he said prosecutors have not yet turned over much evidence to him. A spokesman for the U.S. Attorney’s Office declined to comment on the FISA evidence.

Asked about the allegations, Werksman said, “At this point, I really can’t comment, but we’re going to put forward a vigorous defense and demonstrate that these charges are baseless.”

The FBI said Gartenlaub and his wife sold their Irvine home in February after agents had searched it and are staying at a rental in Laguna Hills.

A Cincinnati native, Gartenlaub has lived in Irvine and Laguna Hills for most of his adult life, his lawyer said.

Over the objection of prosecutors, who asked that Gartenlaub be detained until trial as a flight risk, a federal magistrate judge set bail last week at $400,000. He was released on home detention and is subject to electronic monitoring.

Prosecutors said they worried that Gartenlaub would flee to China, where his wife was born and where the couple have owned property and frequently traveled. At the judge’s order, Gartenlaub surrendered his passport.

Contact the writer: ehartley@ocregister.com or 949-229-5950