BERLIN (AP) — Thieves broke into Dresden's Green Vault, one of the world's oldest museums, early Monday morning, making off with three "priceless" sets of 18th century jewelry that German officials said would be impossible to sell on the open market.

The treasury of Augustus the Strong of Saxony was established in 1723 and today contains around 4,000 objects of gold, precious stones and other materials on display in Dresden's Royal Palace.

Authorities said it appeared the thieves had broken open only one glass case containing three sets of Baroque jewelry made up of dozens of gems each.

"This is a bitter day for the cultural heritage of Saxony," the state's interior minister, Roland Woeller, told reporters.

He said the thieves "stole cultural treasures of immeasurable worth — that is, not only the material worth but also the intangible worth to the state of Saxony, which is impossible to estimate."

Police said they have established a special investigation team, code-named 'Epaulette' and comprising 20 specialist officers, to solve the case. Museum officials said the sets that were stolen included intricate and dazzling brooches, buttons, buckles and other items.

Green Vault director Dirk Syndram stressed that the collections in the museum have "invaluable cultural value" — particularly their completeness.

"Nowhere in any other collection in Europe have jewels or sets of jewels been preserved in this form and quantity," he said. "The value is really in the ensemble."

Police said they were alerted shortly before 5 a.m. by unarmed museum security guards who had spotted two burglars inside the downtown museum on video surveillance cameras.

The first officers arrived on the scene within minutes but the thieves had already fled in a waiting getaway car, which managed to elude immediate attempts to find it in the surrounding area and on the nearby highway, Dresden police chief Joerg Kubiessa said.

Police later confirmed that an Audi A6 matching the description of the getaway car was found burned in an underground parking lot in Dresden.

"It's not just the State Art Collections that was robbed, but us Saxons," tweeted Michael Kretschmer, the governor of Saxony, where Dresden is located. "One can't understand the history of Saxony without the Green Vault."

Investigators suspect that a fire at an electrical junction box near the museum, which took out the streetlights at the time of the robbery, was linked to the crime, police said. The outage affected lights in front of a window through which the thieves gained entrance, somehow getting through bars and safety glass to reach the Jewel Room.

Security footage released by police shows two hooded figures entering the room, then smashing open the glass case with an ax.

"In total, the entire crime only took a few minutes," police said in a statement.

Dresden's State Art Collections director, Marion Ackermann, said it was impossible to estimate the value of the items.

"We cannot give a value because it is impossible to sell," she said, appealing to the thieves not to break the ensembles into pieces. "The material value doesn't reflect the historic meaning."

Woeller pledged that investigators would "do everything in (their) power not only to bring the cultural treasures back, but to capture the perpetrators."

Exhibition rooms at the museum focus on treasures featuring jewels, ivory, silver and amber among other objects.

One of its most famous and precious treasures, the Dresden Green Diamond, is currently on loan with other valuable pieces to the Metropolitan Museum of Art in New York for an exhibit.

The 41-carat green diamond was acquired by Augustus III, the son of Augustus the Strong, in 1742, according to the museum.

The museum said the purchase cost 400,000 thalers, compared to the 288,000 thalers it cost to build Dresden's lavish Frauenkirche church at around the same time.