Police have denied they botched the operation over the robbery of £22m from a Belfast bank.
The van, bottom left, is seen close to the bank
It comes as the serial numbers of 150,000 £10 notes thought to be stolen were released.
It has emerged police missed the robbers by a matter of minutes.
Officers went to the area after reports of suspicious activity near the Northern Bank's headquarters on the night of the raid.
Monday's raid is thought to have been one of the biggest UK cash robberies.
Police have urged other banking institutions, retailers and members of the public to look out for the suspected stolen new Northern Bank £10 notes.
The serial numbers run from BC8500001 to BC8550000, BC9100001 to BC9150000 and BC9350001 to BC9400000.
The IRA has denied involvement in the robbery, the BBC has learned. A senior republican dismissed "any suggestion or allegation that we were involved".
THE £22M RAID
£12m in new Northern Bank £100 and £20 notes were taken
£5m of assorted used NI banknotes were taken
£1.15m of new Northern Bank £100 and £50 notes were among the stolen cash
Four people were held hostage at a house in Poleglass on the outskirts of west Belfast
Two people were held in County Down
A woman was held blindfolded for more than 24 hours
45 detectives are working on the case
Police confirmed that a report of suspicious activity outside the bank was received on the night of the robbery.
It is understood a traffic warden called police to report two men acting suspiciously after a white van was spotted parked in a nearby side street.
A foot patrol had been sent to check out the reported suspicious activity and it would now appear those officers missed the gang by just a few minutes.
Detective Superintendent Andy Sproule said: "Police did receive a call from a traffic warden at 20.13 (GMT). Officers were here within five minutes, unfortunately the van appeared to have gone."
He added: When officers arrived here, there was no evidence of a crime. The gates were closed and it was some two hours later that a crime was reported to police - that wasn't the police's fault.
"It wasn't a botched police investigation and I want to nail that quite clearly at the start."
Police say they cannot yet confirm if the reported van was the one used in the raid.
Detectives have released CCTV footage of the van.
Police put a similar van on display at the robbery scene
Detectives said the possible involvement of paramilitaries was a "key line of inquiry".
They have identified two criminal gangs and three paramilitary factions that they believe are capable of carrying out the robbery.
They are comparing the previous activities and methods used by these groups and comparing that with what happened on Monday evening.
At least 10 men are now known to have been involved in the robbery.
DUP deputy leader Peter Robinson said there was "considerable speculation that the IRA may have been involved".
"If the speculation emerges as the reality, it would deliver a lethal blow to Sinn Fein hopes of being accepted as suitable for government in Northern Ireland," he said.
Police said the robbery was carried out by professional criminals who had "clearly done their homework".
The two bank officials whose families were held hostage are being interviewed in depth by detectives who say the process could take several days.
Police say they want to establish how the gang knew which staff to target.
A female hostage held during the raid raised the alarm after scrambling through a forest.
The robbers stole millions from the vaults of the bank in Donegall Square West on Monday as the families of two bank officials - one at Downpatrick, County Down, and the other at Poleglass near Lisburn - were held hostage.
The bank officials are Kevin McMullan from Downpatrick and Chris Warde from Colinmill in Poleglass.