Detectives are questioning a man over the seizure of drugs and a gun.
Ammunition was also seized during a raid on a house in Poppintree, Dublin.
Cocaine found at the scene is believed to have a street value of more than 20,000 euro and has been sent for forensic tests.
A 9mm pistol and eight rounds of ammunition also seized in the operation will undergo technical examination.
A 30-year-old man arrested at the house is being held under section 30 of the Offences Against The State Act at Ballymun Garda station in the city.
He can be detained for up to 72 hours.
A Garda spokesman said: "A forensic technical examination is under way at the premises and the operation is ongoing."