The U.S. attorney for the eastern district of North Carolina, George Holding, and a spokeswoman for Blackwater did not return calls seeking comment Friday. Pentagon and State Department spokesmen declined to comment.

Officials with knowledge of the case said it is active, although at an early stage. They spoke on condition of anonymity due to the sensitivity of the matter, which has heightened since 11 Iraqis were killed Sunday in a shooting involving Blackwater contractors protecting a U.S. diplomatic convoy in Baghdad.

The officials could not say whether the investigation would result in indictments, how many Blackwater employees are involved or if the company itself, which has won hundreds of millions of dollars in government security contracts since the 2003 invasion of Iraq, is under scrutiny.

In Saturday's editions, The News & Observer of Raleigh reported that two former Blackwater employees — Kenneth Wayne Cashwell of Virginia Beach, Va., and William Ellsworth "Max" Grumiaux of Clemmons, N.C. — are cooperating with federal investigators.

Cashwell and Grumiaux pleaded guilty in early 2007 to possession of stolen firearms that had been shipped in interstate or foreign commerce, and aided and abetted another in doing so, according to court papers viewed by The Associated Press. In their plea agreements, which call for a maximum sentence of 10 years in prison and a $250,000 fine, the men agreed to testify in any future proceedings.

Calls to defense attorneys were not immediately returned Friday evening, and calls to the telephone listings for both men also were not returned.

The News & Observer, citing unidentified sources, reported that the probe was looking at whether Blackwater had shipped unlicensed automatic weapons and military goods to Iraq without a license.

The paper's report that the company itself was under investigation could not be confirmed by the AP.

Meanwhile, Secretary of State Condoleezza Rice ordered a review of security practices for U.S. diplomats in Iraq following a deadly incident involving Blackwater USA guards protecting an embassy convoy.

Rice's announcement came as the U.S. Embassy in Baghdad resumed limited diplomatic convoys under the protection of Blackwater outside the heavily fortified Green Zone after a suspension because of the weekend incident in that city.

In the United States, officials in Washington said the smuggling investigation grew from internal Pentagon and State Department inquiries into U.S. weapons that had gone missing in Iraq. It gained steam after Turkish authorities protested to the U.S. in July that they had seized American arms from the outlawed Kurdistan Workers Party, or PKK, rebels.

The Turks provided serial numbers of the weapons to U.S. investigators, said a Turkish official.

The Pentagon said in late July it was looking into the Turkish complaints and a U.S. official said FBI agents had traveled to Turkey in recent months to look into cases of missing U.S. weapons in Iraq.

Investigators are determining whether the alleged Blackwater weapons match those taken from the PKK.

It was not clear if Blackwater employees suspected of selling to the black market knew the weapons they allegedly sold to middlemen might wind up with the PKK. If they did, possible charges against them could be more serious than theft or illegal weapons sales, officials said.

The PKK, which is fighting for an independent Kurdistan, is banned in Turkey, which has a restive Kurdish population and is considered a "foreign terrorist organization" by the State Department. That designation bars U.S. citizens or those in U.S. jurisdictions from supporting the group in any way.

The North Carolina investigation was first brought to light by State Department Inspector General Howard Krongard, who mentioned it, perhaps inadvertently, this week while denying he had improperly blocked fraud and corruption probes in Iraq and Afghanistan.

Krongard was accused in a letter by Rep. Henry Waxman, D-Calif., chairman of the House Oversight and Government Reform Committee, of politically motivated malfeasance, including refusing to cooperate with an investigation into alleged weapons smuggling by a large, unidentified State Department contractor.

In response, Krongard said in a written statement that he "made one of my best investigators available to help Assistant U.S. Attorneys in North Carolina in their investigation into alleged smuggling of weapons into Iraq by a contractor."

His statement went further than Waxman's letter because it identified the state in which the investigation was taking place. Blackwater is the biggest of the State Department's three private security contractors.

The other two, Dyncorp and Triple Canopy, are based in Washington's northern Virginias suburbs, outside the jurisdiction of the North Carolina's attorneys.