Derry and Strabane police commander Superintendent Gordon McCalmont speaks to press on Monday
Police said they’ll continue to keep the public updated following the discovery, which was made following searches targeting the activity of the New IRA.
Several homes have been evacuated.
The Corn Beef Tin, Central Drive, is open as a rest centre.
Rathmore Roundabout to Fanad Drive is closed with diversions in place.
Police say a “number of stones” have been thrown at officers while the suspicious object is examined.
A PSNi spokesperson said: “We are starting to see a build-up of young people in the vicinity of our policing operation and several missiles have been thrown at officers.
“To prevent anyone getting drawn into disorder we are asking parents and those with influence to come and bring their children home.
“Given the nature of the operation public safety must be a priority.”
Earlier on Monday, the PSNI released pictures of a mortar bomb placed in Strabane they say the paramilitary group is responsible for.
An Improvised Explosive Device (IED) was found by a resident in the Church View area of the town.
“We have a small group of individuals absolutely intent on inflicting harm on our community,” said Superintendent Gordon McCalmont, speaking at a press conference on Monday morning.
“There are small numbers that are not allowing our communities to develop and move on.
“As a district commander, we are concerned as an organisation that this is the seventh attack this year of significance and it’s presenting us with real challenges,” he said.
Chief Constable Simon Byrne has described the attack as an attempt to kill officers and said it’s “a stark reminder why we need to grow PSNI to 7500 officers to grow our presence in communities to deal with this severe threat”.
The deadly New IRA mortar bomb found in Strabane
Police believe the incident may be linked to the hijacking of a Pizza delivery driver’s car in the Mount Sion area on Friday evening.
A number of homes in the Church View area were evacuated following the discovery of the object while it was made safe and removed for further examination.
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