BERLIN -- Hundreds of German special police raided several buildings in Berlin early this morning, arresting four suspects in connection with the brazen heist of a 100-kilogram Canadian gold coin stolen from one of the city's museums earlier this year.

Heavily armed masked police arrested the suspects, one wearing a hood over his head, in Berlin's Neukoelln neighbourhood.

Another nine people are being questioned in the case.

Police say all suspects are related to one another and aged between 18 and 20.

The raids of 13 different buildings lasted several hours, but the gold coin was not recovered.

Carsten Pfohl of the Berlin state criminal office told reporters that police also confiscated clothes and cars to comb for traces of gold.

"We assume that the coin was partially or completely sold," he said.

The Canadian "Big Maple Leaf" coin, worth several million dollars, was stolen from the Bode museum in March.

Police say the three-centimetre thick gold coin, with a diameter of 53 centimetres has a face value of C$1 million. By weight alone, however, it would be worth almost C$4.5 million at market prices.

Experts think the coin may have been melted down already to cash in on the gold. Police also searched a jewelry store in the Berlin neighbourhood, saying they had indications the store may have been involved in the possible sale of the gold.

The thieves were most likely tipped off to the existence of the enormous coin by an acquaintance who worked at the museum as a guard, police said.

At least two burglars broke into the museum at night on March 27, using a ladder to climb to a window from elevated railway tracks. They grabbed the coin, loaded it onto a wheelbarrow and then carted it out of the building and along the tracks across the Spree River before descending into a park on a rope and fleeing in a getaway car.

Police had published footage from surveillance video asking the public for help in finding the thieves.

The coin, which has an image of the Queen on one side and maple leaves on the other, was on loan from a private, unidentified person, dpa reported. It's one of only five that were made by the Royal Canadian Mint.