A pipe bomb has been made safe by the Army in Magherafelt.
The device, which police described as "viable", was found outside a house in the Sandy Braes area just after midnight on Wednesday.
A number of people who had to leave their homes have now returned and the alert is over.
Two other alerts in Belfast, on the Springfield Road in the west of the city and Loopland Gardens in the east, were hoaxes.
Commenting on the Magherafelt incident, DUP assembly member Ian McCrea said: "This device could have resulted in the loss of innocent life if detonated by a child or a passer-by and I am utterly disgusted by this mindless action.
"This incident has caused the local residents a lot of distress and disruption with people being evacuated from their homes so late at night."