Residents still remain out of their homes in Londonderry as army bomb squad experts comb the area.
Overnight alters in Londonderry and Lisburn have both been declared hoaxes.
The security alert in Londonderry began in the Strand Road area this morning after the discovery of a suspicions object last night.
The cordon has been reduced down to a part of Asylum Road between Queen Street and Strand Road but nearby residents who had been evacuated remain out of their homes.
Supt Mark McEwan said: “The security alert began with the discovery of a suspicious object in Bayview Terrace shortly before 10.30pm last night.
“The object was examined by ATO [army bomb squad] and they have declared it a hoax.
“Further daylight searches are required and will be commencing this morning.
“At this time we are investigating a possible link between the alert and a vehicle hijacking in Quarry Street at around 10pm.
“The blame for disruption this alert has caused lies squarely with those responsible for leaving the object in Bayview Terrace and I am thankful to local people for their support and cooperation.
“I would ask anyone with information to contact detectives at Strand Road police station by calling the non-emergency number 101. Or, if someone would prefer to provide information without leaving their name they can contact the Crimestoppers charity anonymously on 0800 555 111.”
Meanwhile, Magheralave Park South in Lisburn had also been closed by police following the discovery of a suspicious object. A number of homes were evacuated whilst the object was examined.
However police declared early this morning that the object had been examined and was also hoax.