A US television news employee has been charged with smuggling artworks and monetary bonds from Iraq.
Items are popping up for sale on the internet
Benjamin James Johnson - an engineer for Fox news - stands accused of bringing into the US 12 paintings taken from a palace belonging to Saddam Hussein's son Uday and also of making false statements to the police.
Mr Johnson, who was embedded with US troops during the Iraq war, was arrested at Dulles International Airport near Washington. Fox says he has been fired.
A US Government official warned returning soldiers and journalists that looting would not be tolerated.
These items are not souvenirs or 'war trophies' but stolen goods that belong to the people of Iraq
Homeland Security Department
"These items are not souvenirs or 'war trophies' but stolen goods that belong to the people of Iraq," Deputy Secretary of Homeland Security Gordon England said.
He was speaking at a news conference where he displayed looted objects including gold-plated weapons.
'Presents from Iraqis'
When stopped by Customs officials, Mr Johnson declared just $20 worth of cigarettes.
But a search of his luggage revealed the 12 paintings from Iraq.
Mr Johnson reportedly told the officials he had been given the paintings by Iraqi citizens, but later admitted that they had been removed from presidential palaces in Baghdad.
The paintings were part of a haul of stolen goods put on display by the US Customs Department.
Several other journalists and one American soldier are also under investigation.
US officials say the paintings themselves are not of any great value.
Customs agents at a US airport believe they have seized at least one item taken from Baghdad museum, which was looted of thousands of valuable artefacts as Saddam Hussein's regime collapsed.
The FBI refused to say at which airport the object had been confiscated or the nature of the artefact, but customs officials across the country have been put on high alert amid suspicions that many of the stolen objects will end up on the US market.
80,000 cuneiform tablets with world's earliest writing
Bronze figure of Akkadian king - 4,500 years old
Silver harp from ancient city of Ur - 4,000 years old
Three-foot carved Sumerian vase - 5,200 years old
Headless statue of Sumerian king Entemena - 4,600 years old
Carved sacred cup - 4,600 years old
Many objects from Iraq, looted both at the end of the first Gulf War in 1991 and during the last, have already started turning up for sale at online auctioneers, experts say.
"You won't find the big, expensive pieces on the internet, but the smaller things that won't command as much attention," Dr Neil Brodie of the UK's Illicit Antiquities Research Centre told BBC News Online.
"It's these pieces that are much harder to track down."
The US has come in for intense criticism from archaeologists and art historians for its failure to protect Baghdad's cultural heritage from looters when lawlessness broke out.
Three White House cultural advisers resigned in protest, and Washington subsequently announced plans to send FBI agents to join Interpol police in the recovery operation, both inside and outside Iraq.
The FBI says it will work closely with art collectors, auction houses, museum curators and online sellers to track down any Iraqi pieces put up for sale.
As well as the national museum in Baghdad, a museum in Mosul was looted and the capital's Islamic Library, which housed ancient manuscripts including one of the oldest surviving copies of the Koran, was ravaged by fire.
The UN's cultural agency Unesco has called the loss and destruction already suffered "a disaster".