A former agent for the FBI and CIA with ties to the popular Detroit area Lebanese restaurant chain La Shish, pleaded guilty Tuesday to faking a marriage to win U.S. citizenship, clearing the way to being hired and given security clearances by the two intelligence agencies.

Nada Nadim Prouty, 37, emigrated to the United States from Lebanon in 1989. She was given U.S. citizenship five years later and began working as a special agent at the FBI's field office in Washington in 1999, according to a criminal information sheet filed in U.S. District Court in Detroit.

While working as a special agent, Prouty improperly searched an FBI computer database for information about her relatives and links they might have to the Hezbollah terrorist organization, the criminal sheet showed. She joined the CIA in 2003 and resigned as part of her guilty plea Tuesday, officials said.

There's no evidence that Prouty was working as a spy on Hezbollah's behalf, two government officials said.

However, "This still continues to be an ongoing investigation," said FBI spokesman Stephen Kodak in Washington.

The case raises questions about hiring practices and background checks by two of the nation's most security-sensitive and secretive agencies.

"This case highlights the importance of conducting stringent and thorough background investigations," Stephen J. Murphy, the U.S. attorney in Detroit, said in a statement. "It's hard to imagine a greater threat than the situation where a foreign national uses fraud to attain citizenship and then, based on that fraud, insinuates herself into a sensitive position in the U.S. government."

Prouty passed a lie-detector test before she was hired by the FBI, which conducted numerous interviews with her relatives and other associates in Beirut and the United States as part of her security background check, Kodak said. But she was not subjected to the more rigorous security screening that the FBI adopted after its 2001 arrest of turncoat Robert Hanssen, who spied for the Soviet Union and Russia over a 20-year period.

"She had a complete, full investigation," Kodak said, referring to the FBI's background check on Prouty before she was hired. He added: "Obviously we have changed certain ways that we do our security clearances."

The CIA largely relied on the FBI's security checks when they hired Prouty, according to a government official familiar with the case who spoke on condition of anonymity because of the ongoing investigation.

“The CIA may have been a little too trusting of the FBI's ability to do a background check, as the bureau's own pre-employment investigation of Prouty would have covered her first years in country," the official said. "That won't happen again."

Prouty sat quietly with her lawyer, Thomas Cranmer, in U.S. District Judge Avern Cohn's courtroom Tuesday afternoon waiting for her case to be called.

Standing before Cohn, Prouty said she understood and agreed to the details of the plea agreement. She left the court building without speaking with reporters.

Cranmer declined to comment on the case.

Several officials with the U.S. Attorney's office and the FBI also were in the courtroom and left without commenting on the case.

According to the court documents, Prouty entered the U.S. on a one-year, nonimmigrant visa.

She lived in Taylor, Mich., with her sister when her visa ran out in 1990. That summer, she paid off an unemployed U.S. citizen, identified in court records as Chris Michael Deladurantaye, to marry her in a civil ceremony in Detroit. But the two never lived together and the marriage was never consummated sexually, the documents show.

The Associated Press was unable Tuesday evening to contact Deladurantaye.

Over the next four years, Prouty claimed she was legally married and living with him as part of her application for U.S. citizenship. She was naturalized in 1994 and filed for divorce in 1995.

Prouty worked off and on between 1992 and 1994 as a waitress and hostess at the popular La Shish Middle Eastern restaurant chain based in the Detroit area before she was hired in 1999 as a special agent in the FBI's field office in Washington.

As an FBI agent, she investigated crimes committed against U.S. residents while overseas. She was not part of investigations into Hezbollah, the Lebanese guerrilla group that the U.S. government has designated a foreign terrorist organization.

Prouty was not authorized to search the FBI database, in 2002, for her name and that of her sister, Elfat El Aouar, and brother-in law, Talal Khalil Chahine, owner of La Shish.

Chahine is believed to have fled to Lebanon in 2005 to avoid federal tax charges. He is accused of skimming more than $20 million in cash and sending it to Lebanon.

Elfat El Aouar was sentenced in May to 18 months in prison for tax evasion.

She and Chahine married in 2000. The couple attended a 2002 fundraiser in Lebanon where Chahine and Sheik Muhammad Hussein Fadlallah were keynote speakers.

Fadlallah, a leading ideological figure with Hezbollah, had been designated by the U.S. government as a global terrorist.

Prouty joined the CIA in 2003. CIA spokesman Mark Mansfield described Prouty as a "midlevel employee" who violated immigration laws long before she was hired by the government.

The CIA is cooperating with the investigation, Mansfield said.

Prouty pleaded guilty to conspiracy, unauthorized computer access and naturalization fraud.

She faces 6 to 9 months in prison as part of the plea, U.S. Attorney's office spokeswoman Gina Balaya said.

Her citizenship has been revoked as part of her plea and she could be ordered to leave the U.S., according to the court documents.

Prouty was released on a $10,000 bond. No sentencing date was set.

Read the full charges against Prouty at the Justice Department Web site.