The New York Times reported Sunday a "few hundred" foreign contractors had been taken into custody, though the U.S. Embassy in Baghdad and U.S. State Department and military officials say no Americans are currently being detained.
The Times said contractors had been detained at the airport in Baghdad and at checkpoints around the capital after the contractors were questioned about documents, including visas, weapons permits and authorizations to drive some routes.
Detentions have lasted from hours to nearly three weeks, though no formal charges had been filed.
The detentions, the Times said, reflect the Iraqi government's asserting its authority after the withdrawal of U.S. troops in December.
After the American troops pulled out, the Iraqi government stopped issuing and renewing numerous licenses and other authorizations, leading to some contractors being detained for having expired documents.
New limitations also have been imposed on visas, giving some contractors just 10 days to leave Iraq or face arrest.
Latif Rashid, a senior adviser to Iraqi President Jalal Talabani, told the Times Iraq is closely monitoring security contractors because of mistrust of them.
"We have to apply our own rules now," he said.
Many Iraqis recall violence involving private sector workers, particularly a 2007 shooting in Baghdad in which Blackwater contractors killed 17 civilians.
The U.S. Embassy employs 5,000 contracts to protect its 11,000 employees and to train the Iraqi military on equipment the United States has sold the country.
In a statement, an embassy spokesman said the detentions and visa delays are often the result of inexperience in the government's bureaucracy.