Police in Germany were investigating Monday after professional thieves staged a daring early morning $1.1 billion heist at one of the world’s oldest museums.

The two crooks made off with three “priceless” ensembles of early 18th-century jewelry in diamond, ruby and emerald on display at the Dresden Green Vault, which was closed at the time, Reuters reported.

Police responded after a security camera spotted two men breaking into the museum through a window at 5 a.m., triggering an alarm.

By the time they got there five minutes later, the thieves were gone, according to Reuters, which quoted Bild newspaper as saying the haul was worth up to 1 billion euros ($1.1 billion).

“We are talking here of objects of immeasurable cultural value,” museum director Dirk Syndram told a news conference.

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Marion Ackermann, head of the Dresden state museums, said the stolen jewels “cannot be sold on the art market legally — they're too well known,” according to the BBC.

She feared the thieves might try to break up the ensembles.

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Police are trying to determine if the thieves set fire to an electrical junction box near the museum that took out the streetlights at the time of the robbery, said Volker Lange, head of the law enforcement probe.

He said the outage affected lights in front of a window through which the thieves gained entrance, somehow getting through bars and safety glass.

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Lange said they were also trying to determine whether an unregistered car, found on fire nearby with all four doors open and smelling of gasoline, may have been the getaway car.

The Associated Press contributed to this report.