Art experts warn that a hoard of royal jewelry taken during a daring heist at one of Germany's most famous museums could disappear forever with the pieces being broken up and their gemstones removed for sale.

Dozens of items stolen from an 18th century collection at Dresden's Grünes Gewölbe museum, or Green Vault, are so identifiable that it would be very difficult for the thieves to sell them on the open market, said Julian Radcliffe, chairman of the world’s largest private database of lost and stolen art, The Art Loss Register.

"If they broke them down, they would be able to sell individual diamonds for a price," he said.

But even the loose stones may prove a challenge for the thieves to pawn off.

This piece was among the items stolen during a robbery from the Green Vault in Dresden on Monday. Juergen Karpinski / AFP - Getty Images

"Because these are 18th century cut, they are not common for current use," Radcliff said. "There is a danger they might try to re-cut them."

The collection was founded in the German state of Saxony by August the Strong, a Saxon ruler who later served as the king of Poland, and contains items that hold invaluable cultural value, museum officials said.

“The fact that these are precious cultural objects to Saxons and the world means nothing to these criminals,” said Christopher Marinello with Art Recovery International, a lawyer and expert in recovering stolen, looted and missing works of art. "They are cold-hearted cultural barbarians who will steal from their own mother."

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Police did not provide a full list or detailed description of all the stolen jewelry, but pictures show several brooches, a sword and a necklace among the stolen items.

Some German media have reported that the value of the jewelry could top hundreds of millions of euros, while museum officials say the items are "priceless."

The director of the Dresden State Art Collections, Marion Ackermann, said it’s impossible to describe the material value of the stolen artifacts because their historical significance is much greater.

“We cannot put a value on it because it’s unsellable,” Ackermann said. “There is no financial value we work with.”

So the value put on the stolen jewels by the press is purely theoretical, Radcliffe said. In fact, putting a price on them can be misleading, he added.

"This type of jewelry collection never comes onto the market, and therefore nobody knows what it would achieve if sold," Radcliffe said.

“Whatever the value is, if these items are broken down or sold individually, they would be worth pennies compared to their true value and the important thing is to get them back intact,” he said.

Museum officials hope to release a full list of the missing items on Wednesday. They were able to visit the crime scene on Tuesday and found out that more pieces were left behind by the thieves than they initially thought.

The sword of the diamond rose is another precious artifact stolen during the robbery on Monday. Polizeidirektion Dresden / Reuters

Details of the stolen items could be entered into a database of stolen artifacts in the hopes they can raise the alarm of suspicious buyers, Radcliffe said, but if the criminals find it too difficult to monetize them, there is a chance they could simply abandon them.

“The Swedish crown jewels, which were stolen several years ago, were recovered when they were left in a bin, so sometimes the thieves find that these are too hot to hold.”

Meanwhile, Marinello said it’s paramount for law enforcement to act fast if there is to be any hope of recovering the artifacts in their original form.

“There is no time to lose,” he said.

The police also need to make it known that they want these pieces returned intact and if they are broken up, the penalties will be more severe, Marinello added.

German investigators, who are still analyzing the crime scene, told NBC News on Tuesday the suspects are still on the run. They didn't detail their next steps, but did say that a burned-out car found two and a half miles away from the museum was tied to the break-in.

“If they are going to issue a reward for information, it should come now before the gold is melted down and stones and diamonds are removed. This needs to be treated like a hostage situation,” Marinello said.