A man and a woman have been arrested by police investigating a raid on a Securitas depot in Kent in which armed robbers got away with up to £50m.
The 7.5 tonne lorry used by the robbers was caught on CCTV
A man aged 29 and woman aged 31, arrested in Forest Hill, south London, are being held at Kent police stations.
They are being questioned on suspicion of conspiracy to commit robbery.
Earlier a £2m reward was offered for information about the raid, which police said was executed with military precision by professional robbers.
"These arrests are significant developments and are very positive and directly related to the investigation," said Kent Assistant Chief Constable Adrian Leppard.
He said the man and woman were arrested at separate addresses.
The incident room has received more than 400 calls from the public with information which is being passed to detectives.
People are urged to keep trying the numbers if lines are busy.
Police are keen to trace the movements of what is believed to be a former Parcelforce red van found abandoned at the Hook and Hatchet pub in the village of Hucking.
They believe it may have been used in the abduction of the depot manager Colin Dixon 51, his wife Lynn, 45 and eight-year-old son Craig.
Colin and Lynn Dixon were taken to the depot with their son
It is the fifth vehicle police believe to be connected with the robbery, following a debriefing with Mrs Dixon who remembers having been inside the vehicle at some stage.
The security firm and insurers put up the reward to try to tempt criminals with information to come forward.
It is thought to be the biggest such reward offered in the UK.
Mr Leppard said: "This is a terrifying crime committed by professional and organised gangsters.
"It is important to remember that this is a dangerous armed gang, which put a young family, including an eight-year-old boy, and 14 staff at the depot through a terrifying ordeal."
The assistant chief constable said at least £25m cash was missing, but the amount taken could be as high as £50m.
'Armed and dangerous'
The precise total will not be known until auditors have been allowed into the site.
Police said the gang of at least six men, some wearing masks and carrying handguns, were "armed, dangerous, and violently threatening".
They first struck on Tuesday evening, when Mr Dixon was abducted by men posing as police officers.
Two further gang members, again posing as police, visited the manager's Herne Bay home telling his Mrs Dixon and their son he had been involved in an accident, before taking them to a west Kent farm where he was held.
The armed gang forced the manager to let them into the depot
The family was then taken to the Vale Road depot in Tonbridge where Mr Dixon was forced to let one of the gang in.
Fourteen staff members were tied up and kept in a room.
The money was loaded on to a white Renault lorry before the gang drove off early on Wednesday.
Anyone with any information is asked to contact police incident room on 01622 652361 or 01622 652366.
1) Security depot manager abducted by gang members posing as policemen, close to the Three Squirrels pub, near Stockbury
2) The manager's wife and son, aged eight, are taken from their home in Herne Bay, after being told he was in an accident
3)Wife and son taken to farmhouse at unknown location in west Kent. The manager is eventually taken there as well
4) Armed and masked robbers raid the depot in Tonbridge