The two suspects, a Moroccan-born Dane and an Iranian citizen, were believed to have links to criminal gangs in Denmark. Police said the investigation was not related to terrorism.
The suspects were arrested Monday, five months after police found 483 grams, or a little over a pound, of a plastic explosive, three detonators and a mobile phone that had been rigged so it could set off a bomb.
Police also found a submachine gun and three pistols as well as 336 grams (12 ounces) of heroine and 298 grams (10 ounces) of cocaine hidden at the bottom of an elevator shaft.
Investigators kept the discovery secret as they were tracking down the suspects.
The suspects were not identified.