Former Interior Secretary Gale Norton, until now, has escaped the cross hairs in a series of scandals that plagued her federal agency.

Norton never was implicated in cases ranging from Interior employees illicitly having sex and using drugs to officials serving prison time for obstruction of justice.

But with a private-sector job in the oil-shale industry, Norton finds herself the target of a criminal investigation over her former agency's dealings with her current employer, petroleum giant Royal Dutch Shell.

Norton is a longtime Colorado political fixture and former state attorney general.

Shell officials Thursday confirmed media reports that the Justice Department is investigating Norton, who now serves as legal counsel in Shell's metro Denver-based "unconventional oil" unit.

That division oversees Shell's development of petroleum from oil shale and oil sands. Shell's research and development project for oil shale in northwest Colorado is considered one of the nation's most-advanced forays into the still-experimental technology.

Experts have estimated that oil-shale deposits in Colorado, Utah and Wyoming could yield at least 800 billion barrels — more than three times the oil reserves of Saudi Arabia and worth $58 trillion at current oil prices.

A Shell spokeswoman said that neither the company nor Norton would comment further on the investigation. Federal law enforcement and Interior officials said the probe focuses on the department's 2006 decision — when Norton was head of the agency — to award Shell three potentially lucrative leases for oil-shale development on federal lands in Colorado.

Norton resigned two months later, then accepted a job with Shell in Colorado in December 2006. The investigation seeks to determine whether Norton violated laws that prohibit federal employees from steering contracts to, and discussing employment with, companies that could benefit from government deals.

"Public officials using their public office for personal enrichment is a serious breach of the public trust," said Mary Boyle of Common Cause, a Washington-based government watchdog.

Boyle said that although Common Cause has no information on whether Norton acted improperly, the federal investigation presents "troubling allegations."

An investigation last year by the Interior Department's inspector general found that employees of the agency's Lakewood-based Minerals Management Service had sex, smoked marijuana and used cocaine with energy-industry employees they were supposed to be regulating.

J. Steven Griles, Norton's deputy at Interior, in 2007 was sentenced to 10 months in prison and fined $30,000 for obstructing a federal investigation into lobbyist and convicted felon Jack Abramoff.

Griles' former girlfriend, Italia Federici, was a fundraiser for Norton's 1996 campaign for U.S. Senate in Colorado and a former aide to Norton. Federici in 2007 was sentenced to two months in a halfway house and four years of probation and was ordered to pay $74,000 in restitution on a conviction of tax evasion and obstruction.