A gang who escaped with €600,000 during a raid on a cash van in Dublin on Tuesday drove a JCB-style forklift used in the attack from Balbriggan to Dublin along the M1 motorway just hours before the raid.
Senior gardaí said they were "astounded" the gang drove the bright yellow teleporter - a type of forklift - for such a distance to a crime scene.
"We've had a lot of witnesses coming forward saying they saw it on the M1. Whoever was driving it seems to have made no effort to hide what they were doing or where they were going," said a senior Garda source.
The raiders drove the vehicle, which was stolen from a building site in Balbriggan, to Carraroe Avenue, Donaghmede.
They parked it there and put road works signs around it to make it appear as if a job was about to start.
The gang then waited until a Securicor van arrived at nearby Donaghmede Shopping Centre to service two ATM machines at 1.30pm.
When the van arrived, one of the raiders rammed the front of it with the teleporter, breaking the windscreen.
Two other gang members were waiting in a car nearby. These joined the driver of the teleporter in climbing into the Securicor van and stealing bags of money containing €600,000.
The three men, at least one of whom was armed, then sped from the scene in a car. The vehicle was discovered and a suspect arrested at Bayside Boulevard, Bayside, soon after the attack. The man, who is in his early 50s, lives in Bayside.
Seven houses were raided around Bayside yesterday morning by detectives investigating the robbery, the biggest in the State for a year. There were no arrests.
Senior Garda sources said some of the houses were owned by known armed criminals, none of whom were at home when gardaí moved in at dawn.
However, a number of items, including gloves and balaclavas, were discovered in the car found in Bayside. Gardaí believe these were used by the raiders, and have sent them to be forensically examined.
The suspect still being questioned at Coolock Garda station is being held under Section 30 of the Offences Against the State Act. He can be detained without charge until around 2pm today, after which gardaí must charge him or apply to the courts to detain him for a further 24 hours.
Gardaí in Coolock have appealed for anybody who may have seen the yellow teleporter travelling from Balbriggan to Donaghmede on Tuesday to come forward. They can be reached at (01) 6664200.
