Thieves are believed to have stolen jewels worth upwards of a billion dollars from Dresden’s historic Grünes Gewölbe museum, which translates to the “Green Vault,” although it has yet to be confirmed exactly what was taken.

According to Bild, perpetrators are thought to have ignited a fire at a nearby power distributor at 5 a.m. to cut the museum’s electricity supply, which in turn disabled alarms. Thieves are then said to have bent iron bars on a ground-floor window to break into the historic museum.

“We can confirm a break in the Green Vault,” police spokesman Thomas Geithner said. “Investigators are on the scene and the perpetrators are on the run.”

Dozens of police cars could be seen outside the building, located in the Dresdner Residenzschloss, Dresden’s royal palace, while investigators could be seen trying to gather what evidence they could.

What is currently known is that thieves escaped via a sedan and only targeted jewels, gems and diamonds, leaving bulkier items such as paintings behind.

The collection is made up of 10 highly decorated rooms, containing about 3,000 pieces of jewelry in addition to ornate items such as a 25-inch figure of a Moor studded with emeralds and a 648-carat sapphire—a gift from Russia’s Peter the Great.

Its most valuable item—a unique 41-carat naturally green diamond—is currently on loan to the Metropolitan Museum of Art in New York.

Minister President of Saxony Michael Kretschmer voiced outrage at the crime, saying that “not only were the state art collections burgled, but the people of Saxony too.”

“The valuables housed in the Green Vault and Residenzschloss were hard-won by the people in the Saxony Free State with difficulty, over many centuries.

“One can not understand the history of our country, of our Free State, without the Green Vault and the State Art Collections of Saxony.”

The theft is by far the largest heist in history, surpassing the raid on the Isabella Stewart Gardner Museum in Boston in 1990. Then, two thieves dressed as police officers responded to a disturbance call and, once inside, they tied up all the security guards on site.

Within the space of an hour, they walked out with 13 paintings—including some by Rembrandt, Manet and Degas—that were valued at a collective $500 million.