A third person has been arrested by detectives investigating the raid on a Securitas depot in Kent in which armed robbers got away with up to £50m.
Police said the woman, 41, was held at a building society in south-east London on suspicion of handling stolen goods.
A man, 29, and a woman, 31, were arrested in south London on suspicion of conspiracy to commit robbery.
Three vehicles involved in the robbery have been found, but not the lorry used to transport the money, police said.
Officers said the depot manager's car, the Nissan Almera, had been found, together with the Volvo used to pull over Colin Dixon.
The Nissan was found parked at the Cock Horse pub in Detling and the Volvo was found burning near Maidstone.
A red van, thought to be a former Parcelforce vehicle which was used to hold Mr Dixon, his wife, and eight-year-old son, has also been found at the Hook and Hatchet pub in Hucking in Kent.
Forensic tests are taking place on all of the vehicles.
A £2m reward has been offered for information about the raid.
Kent Police Assistant Chief Constable Adrian Leppard said the robbery was executed with military precision by a professional gang operating at the "top level" of organised crime.
Police believe this burnt-out Volvo was used by the robbers
"These arrests are significant developments and are very positive and directly related to the investigation," he said.
The man and woman were arrested in Forest Hill at separate properties, which are being searched and subjected to forensic tests.
The 41-year-old woman was detained at the Portman Building Society in Bromley on Thursday.
All three people are being questioned at police stations in Kent.
An incident room had by Thursday night taken more than 400 calls from the public, with information which is being passed to detectives.
Mr Dixon, 51, and his family were subjected to what police described as a "terrifying" ordeal lasting at least six hours.
They were snatched from their Herne Bay home and taken to a remote Kent farmhouse where the gang threatened to shoot them unless Mr Dixon complied with their demands.
A red van with Parcelforce markings was found at a pub in Kent
The family was then taken to the Vale Road depot in Tonbridge and Mr Dixon was forced to let one of them in.
Fourteen staff members were threatened, tied up and kept in a room while the money was loaded on to a white Renault lorry before the gang drove off early on Wednesday.
The security firm and insurers have put up the £2m reward to try to tempt criminals with information to come forward.
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."
He said at least £25m in cash was missing, but the amount taken could be as high as £50m.
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, at 1830 GMT on Tuesday 21 February.
2 At around the same time, the manager's wife and eight-year-old son are taken from their home in Herne Bay to a farmhouse somewhere in west Kent, where the manager is eventually taken as well.
3 At 0100 on Wednesday, the manager and family are taken to the Tonbridge depot where he is forced to give access to the armed and masked robbers, who leave with their haul at 0215.
4 On Thursday, an abandoned red van that may have been used during the abductions is found at a pub in Hucking.
5 The same day a man and woman are arrested in Forest Hill, south London, on conspiracy-related charges.
6 Later a woman is held at a building society in Bromley.
7 Volvo saloon believed to have been used by robbers posing as police found burning in Burberry Lane in the village of Leeds on Thurs evening.
8 Silver Nissan Almera car belonging to depot manager found at the Cock Horse pub in Detling on Thurs evening.