Robbers who stole up to Ј50m from a Securitas depot in Kent left Ј1.3m in one of their vehicles.
The abandoned Transit van also contained guns, balaclavas and body armour, police have revealed.
In a series of raids on Sunday, police made a sixth arrest. The man, aged 49, was later released on bail.
Officers leading the investigation said on Sunday the robbers were making mistakes because they were under pressure and the net was closing in.
All those arrested have now been released on police bail.
Earlier on Sunday, police said 14 cages - believed to have been used to transport the cash - had been found at Detling, near Maidstone.
Body armour
Assistant Chief Constable Adrian Leppard, of Kent Police, said he was very pleased with how the investigation was progressing.
Police also said a red Vauxhall Vectra, found burnt out, could have been used in the raid last Wednesday.
The Vectra was found next to a Volvo saloon, in Leeds, near Maidstone, that was also burnt out and might have been used to abduct depot manager Colin Dixon in the first stage of the robbery.
Mr Leppard confirmed the items found in the van, in the car park of the Ashford International Hotel, Ashford, included jackets that were similar to body armour.
'Under pressure'
"This discovery is important because of the descriptions we have of the robbers," he said.
"Leaving firearms, clothing and cash in the van suggests to me that there are people in the gang who are now making mistakes.
"They're under pressure and we want to keep the pressure on. I am very encouraged at this stage by the progress we are making. The net is closing in."
(BBC)
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