BELFAST, Northern Ireland — Northern Ireland police say they have arrested four people suspected of organizing an Irish Republican Army letter-bomb campaign.
Hours after Wednesday's arrests in Londonderry, masked men loaded a suspected bomb on to a truck and ordered the driver to park it outside the city's police headquarters. Police evacuated a nearby school and businesses but could not confirm whether the threat was genuine.
Those arrested — men aged 46 and 35, and women aged 44 and 21 — are suspected of mailing at least 10 bombs over the past year. All were detected and dismantled safely.
Targets in Northern Ireland and England included police commanders, a prison governor, a state prosecutor's office, British Army recruitment centers, and Northern Ireland's secretary of state.
Several small IRA factions remain active in Northern Ireland.