BAGHDAD, Iraq - More evidence has surfaced that the looting of the National Museum was carried out in part by professional art thieves who used chaos as cover to make off with artifacts sought by private collectors, museum officials said.

They said financiers from countries like Saudi Arabia, Iran and Jordan have been paying people since the end of the Persian Gulf War in 1991 to smuggle specific items from the sites of archaeological digs around the country.

They are part of a shadowy network that officials in the art world say primarily sells stolen works to wealthy private collectors.

"That is our biggest fear," said Dr. Donny George, the director of research studies at the museum. "That these things that were stolen will go to private collectors and we will never see them again."

He said new signs had emerged in recent days that expert thieves were involved in the looting that followed the fall of Saddam Hussein's government. They passed by a copy of a piece called the Code of Hammurabi because they knew the copy was not worth very much, he said.

George said the museum had prepared for the war by moving many items into underground vaults, but many of those vaults had been broken into. It appeared, he said, that the thieves knew their way around the vaults.

As the city begins to calm down and as experts assess the damage to the museum, officials said they had discovered some interesting clues.

One official showed a reporter the identity cards of some employees who he said were involved in looting. He also showed a set of keys that he said were used.

The nature of the robbery, he said, suggested that outsiders had enlisted low-level museum employees to help them.

At a news conference, Dr. Jaber Khalil, chairman of the state board of antiquities, displayed some tools that were used in the robbery, including picks, hammers and chisels - not the kind of equipment common in the neighborhood around the museum.