Republican paramilitary group Arm na Poblachta (ANP) is suspected of involvement in a failed hijacking in Derry at the weekend.
A major security alert was launched after masked and armed men attempted to hijack a car in Hollymount Park area at approximately 9.35pm on Friday.
The following day a suspicious device, which police have since described as viable, was discovered in the Corrody Road area of the city, near the grounds of Doire Trasna GAA club.
The initial alert was raised after three masked men armed with knives and a firearm approached a fast food delivery driver and attempted to hijack his vehicle.
The suspects later ran off in the direction of Corrody Road, where the suspect device was later found.
Four men, aged 54, 34, 32 and 29 arrested after the alert was raised have since been released.
The group known as ANP is believed to have been behind the alert.
It claimed responsibility for a bomb alert in Derry last November after a delivery driver was hijacked in the Curryneirin area of the Waterside and forced to drive a bomb to a PSNI station.
In a statement to The Irish News, the group later said the home-made device had been left on a 60 minute timer.
Earlier this week the PSNI said a "working line of enquiry" is that the recent incident is linked to the security alert last November.
In the days before that attack the New IRA launched and Improvised Explosive Device (IED) at a PSNI car in Strabane, Co Tyrone.
