Dresden’s famed Green Vault, one of Europe’s greatest collections of treasure, has been robbed despite security measures said to be like Fort Knox’s. The exquisite collection of jewels and other historic items was raided early this morning, November 25. At least two thieves targeted the most historical part of the historic vaults in the center of the east German city. The value of the missing pieces could be worth millions—or even a billion dollars—according to some reports in German media.

The Grünes Gewölbe, or the Green Vault, was ransacked around 5 a.m. According to the German newspaper Bild, the power supply to the building caught fire nearby around the time of the theft, that caused the street lights nearby to go out, as well as a possible power outage at the vaults. (The connection between the two incidents is still being investigated). Two thieves then entered through a small window into the historic museum, taking mostly jewelry and leaving behind heavier objects. The suspects, which according to one report made off in a limousine car, are still at large. First responders were on the scene within five minutes of an emergency call made by the guards.

Though authorities are still evaluating the number and estimated value of the pieces that have been lost, Bild suggests it could total more than €1 billion ($1.1 billion). If that is the case, it would make it the largest museum heist in history, surpassing the theft of Old Masters from the Isabella Stewart Gardner Museum in Boston. At a press conference this afternoon, Marion Ackermann, general director of Dresden’s state art collections, said it was likely impossible to put a value on the stolen items due to their historic cultural value. Among the stolen items is an 18th-century diamond set once owned by Augustus the Strong, who founded the museum in 1733.

Dresden investigators have reached out to the Berlin authorities to look into a possible link between the two cities.

Picture taken on April 9, 2019 shows the Jewel Room ( Juwelenzimmer), one of the rooms in the historic Green Vault (Gruenes Goelbe) at the Royal Palace in Dresden. Photo: Sebastian Kahnert/dpa/AFP via Getty Images.

The Green Vault is now part of the Dresden State Art Collections. It is boasts Europe’s largest collection of more than 4,000 mainly Baroque treasures, including pieces made of gold, rare stones, and diamonds, as well as royal jewelry and other treasures. The items are held in high-security rooms, with 3,000 of the pieces held in the historic 17th-century vault that was targeted by the thieves. The late Martin Roth, the former director of the Dresden State Art Collections, said in 2010: “The Green Vault is secured like Fort Knox.”

Saxon state premier Michael Kretschmer denounced the crime: “Not only the state art collections were robbed, but we Saxons,” he said. “The treasures that can be found in the Green Vault and in the Residence Palace have been hard won by the people in the Free State of Saxony over many centuries.” He added: “One cannot understand the history of our country, our Free State, without the Green Vault and the State Art Collections of Saxony.”

One star jewel the thieves missed is the 41-carat diamond known as the Dresden Green. It one of 17 objects from the Green Vault currently on loan to the Metropolitan Museum of Art in New York.