NEW YORK, NY.- The break-in looked like the work of professionals.

It began after midnight on Nov. 22, 2022, when someone cut fiber optic cables at a telecommunications center in the small German town of Manching, in Bavaria, knocking out internet and telephone connections in 13,000 households.

Then, just before 1:30 a.m., the Celtic and Roman Museum was broken into. Within nine minutes, thieves had pried open two locked doors and a display case, police said.

When museum staff members arrived in the morning, they found the most valuable artifacts in the building were gone: a cache of 483 ancient gold coins, which were believed to date back to roughly 100 years before the birth of Jesus.

One official said the coins, along with a chunk of gold that was also stolen, could be worth $1.7 million, although much less if melted down.

On Thursday, Bavarian state criminal police said that they had arrested four men suspected of carrying out the theft after a monthslong investigation by a 25-member task force turned up a trace of DNA on an unspecified item at the scene.

“The arrest of this professional gang of burglars is due to the highly committed and meticulous work of the police and public prosecutor’s office,” Bavaria’s interior minister, Joachim Herrmann, said in a statement. “The investigation into the whereabouts of the gold treasure will be continued at full speed.”

The deputy head of Bavaria’s state criminal police office, Guido Limmer, told reporters in Munich that authorities had examined 18 lumps of gold that were recovered this week, The Associated Press reported.

Each is believed to be the result of four coins being melted down, he said.

“We know that about 70 gold coins have apparently been lost irretrievably in their cultural and historical significance,” Bavaria’s state culture minister, Markus Blume, said, according to the AP. “But that means that, of course, there is still hope of perhaps being able to find the rest of the gold coins, and so the majority of the gold treasure.”

The coins had been unearthed in 1999 during a dig at an ancient Celtic settlement known as the Oppidum of Manching.

The trove is considered the biggest cache of ancient Celtic gold discovered in the 20th century. It remains a mystery why so much gold was stored in one spot and how it ended up at the site.

The coins were the pride of the Celtic and Roman Museum, a small archaeological institution that showcased them and other artifacts discovered in the region.

After the coins were stolen, investigators, including a police dive team, conducted extensive searches around the museum, Bavarian police said in a statement.

During those searches, two blue crowbars, pruning shears and a cutting tool were found in a nearby pond and in the Paar River, the statement said. Investigators also found a radio antenna next to the museum.

The items were forensically examined, and a DNA sample was obtained, the statement said.

Investigators entered the sample into national DNA databases in Germany and in neighboring countries and found matches with similar thefts throughout Germany and Austria, the statement said.

In several of those thefts, cables had also been cut to circumvent alarm systems. The thefts had other similarities, the statement said.

The burglars wore black overalls with balaclavas and each had identical crowbars, screwdrivers and an angle grinder with several cutting discs, the statement said, without elaborating on how investigators gleaned those details. The thieves also used a radio jammer to disrupt alarm systems.

Investigators examined case files for each of the thefts, which led them to a 42-year-old man from Schwerin in northern Germany. He was believed to have been involved in a burglary in 2018 in the German state of North Rhine-Westphalia, Bavarian police said.

Further investigation led police to a 46-year-old German man and a 50-year-old man, also living in Schwerin.

Police said three men were arrested on Tuesday, right after one of them met with a 43-year-old man from Berlin, who was carrying 18 gold nuggets in a plastic bag. He was also arrested.

An analysis of the nuggets revealed that they contained a mix of gold, silver and copper that corresponded to the composition of the gold coins that had been stolen, officials said.

The four men were charged with aggravated gang theft involving damaged property and disrupting telecommunications systems, the statement said.

Their names were not released, and it was not immediately clear if they had lawyers.

As part of the investigation, police searched more than two dozen apartments, businesses, garden plots, a boathouse and a vehicle, the statement said.

They seized masks, “burglary tools,” backpacks, mobile phones, jammers and cash, the statement continued.

Although authorities did not release more information about the jammers, such devices can be used to block 911 calls, cellphone service, police radar and Global Positioning Systems, according to the Federal Communications Commission.

This article originally appeared in The New York Times.