Gardaí investigating the discovery of an explosive device in a car on the M50 motorway in Dublin last night believe it may be linked to a campaign by the Continuity IRA against drug dealers in Dublin city.

The bomb was discovered when gardaí stopped and searched the vehicle travelling northbound near the West Link Toll Plaza shortly after 10pm.

When gardaí confronted the driver of the car, he jumped out and warned them that there was a bomb in the car and that it was primed.

An Army Explosives Ordance Disposal team was called in following the discovery of the device and a controlled explosion was carried out.

A 24-year-old man was arrested at the scene while a 56-year-old man was arrested later in Ronanstown. Both men were being held at Clondalkin Garda Station.

A section of the motorway between the Blanchardstown and Palmerstown exits was closed for four hours while the operation was continuing.

Staff unaware of operation: NTR director

The managing director of National Toll Roads, Kyran Hurley, said tollbooth staff did not know in advance about last night's garda operation at the West Link Toll Plaza.

There were ten staff manning the plaza at the time of the incident.

However, speaking on RTÉ Radio’s Morning Ireland, Mr Hurley said staff are used to incidents at a minor level in the lanes and are trained in how to handle these incidents.

He said there was no undue concern amongst staff at that incident, and the evacuation of staff happened in accordance with a normal fire drill exercise.