The search in the Inver Road area is linked to the arrest of a serving Royal Marine last week.
CiarÃ¡n Maxwell, who is from the town, was arrested in Somerset as part of the investigation after searches in Larne and Devon.
The 30-year-old marine is still being questioned.
The Metropolitan Police have until 12:20 BST to charge or release Mr Maxwell after his detention was extended by a London court on Friday.
Some homes and at least one business were evacuated while searches were carried out on Tuesday, said DUP councillor Paul Reid.
Larne's Town Park was also closed off by police, but has since reopened.
Meanwhile, police investigating dissident republican activity are questioning a 27-year-old man.
He was arrested on Monday morning in Larne.
His arrest is understood to be connected to the discovery of two arms dumps near the County Antrim town earlier this year.
In March, the PSNI said they had uncovered a "significant terrorist hide" of bomb-making components and explosives at Carnfunnock Country Park.
Among the items recovered were wiring, circuit boards, partially constructed power timer units and a small quantity of explosives.
In May, a second significant arms cache, including an armour-piercing improvised rocket and two anti-personnel mines, was found at Capanagh Forest, near Larne.
Both finds were thought to be linked to dissident republican paramilitaries.
Parts of Larne in County Antrim remain sealed off for a second day while police continue to search for evidence of dissident republican terrorism.