LONDON (AP) — Police say they have found large quantities of explosives after searching 12 properties in Northern Ireland.

The head of the Police Service of Northern Ireland's crime operation unit said Tuesday that "a significant amount of terrorist material" had been uncovered in searches that began two weeks ago in the Larne area north of Belfast.

Assistant Chief Constable Will Kerr said the material included "explosive devices, chemicals for use of bomb making, ammunition, and a firearm."

A royal marine with connections to Larne was arrested last week and charged with terror-related offenses involving Northern Ireland.

Officials have warned that dissident republicans who reject the peace process pose a substantial threat of terrorist attacks.