Gardai were last night trying to find the manufacturer of an explosive device left outside the Dublin headquarters of Shell Ireland.
The device, which contained homemade explosives, was planted in a tin inside a carrier bag that had been dumped outside the front of Corrib House at Lower Leeson Street.
It was described as small but viable and had been set on a timer to explode.
Gardai believe the device had been left there to send a sinister threat to Shell rather than to create much damage, if it had exploded.
The tin also contained other items such as a battery and clock but was unlike the spate of devices that have been planted by crime gangs in the capital in the past couple of years.
Gardai called in an Army bomb disposal team after the device was spotted around 10pm on Monday.
The remains of the device were later handed over to the garda technical bureau for forensic examination.
A Shell Ireland spokesman described the attack as a sinister development and said the company was seriously concerned by the threat posed to its staff and the general public.
"The work currently being undertaken on the Corrib project has all the necessary consents and permissions required by the various statutory bodies, which oversee the project," the spokesman pointed out.
"We remain open and willing to talk to any individuals or groups, who continue to have concerns about our project," he added.
The Shell to Sea Campaign, which has been protesting against the pipeline in county Mayo, denied any connection to the improvised device and said its members were committed to peaceful public protest.
Gardai last night stepped up surveillance and patrolling around the Shell headquarters last night as a result of the incident.