Police are continuing to search an isolated farm which could be linked to the £53m Securitas cash depot robbery in Kent.
Depot manager Colin Dixon and his wife and young son were taken to a remote farm building when they were abducted before the armed robbery a week ago.
Scores of officers are scouring land and buildings at the premises in the village of Staplehurst.
Meanwhile, police are holding six people in custody over the robbery.
Magistrates granted police a further 24 hours to question four suspects on Tuesday evening.
Seven other people arrested in connection with the inquiry have been bailed.
Police activity began on Sunday at Elderden Farm in Staplehurst, which is owned by businessman John Fowler.
Staplehurst: Police searching farm
Herne Bay: Where heist began with depot manager's wife and son kidnapped from home
Stockbury: Depot manager kidnapped from his car
Tonbridge: Cash depot raided by gang
The area in Chart Hill Road was surrounded by more than a dozen police vehicles on Wednesday.
Underwater divers, specialist search teams and vehicle recovery units have been working at the farm buildings and surrounding fields.
Officers could be seen walking along in formation conducting a fingertip search of the undergrowth.
Several vehicles were also towed away from the farm grounds for inspection.
Staplehurst lies 10 miles (16km) south of Maidstone - on the main route between Kent's county town and Hastings - and is surrounded by a huge expanse of farmland.
In other developments, a white Renault lorry believed to have been used during the raid in Tonbridge has been recovered from an undisclosed location.
Forensic tests are being carried out on the vehicle.
Road checks took place in Tonbridge, Faversham and Herne Bay on Tuesday evening, with officers stopping more than 600 vehicles and asking drivers if they remembered seeing anything to do with the raid.
Assistant Chief Constable Adrian Leppard said: "I am very encouraged by the response from members of the public."
Roadside checks were carried out at various locations in Kent
Securitas confirmed on Wednesday that its staff had returned to work at the premises in Vale Road, after a week of police activity and an audit of the amount of money stolen.
Company spokesman Carl Courtney said: "The depot is back up and running 24 hours a day. The first shift came in some time after midnight.
"We are just trying to get back to normal. It's obviously a big disruption to all of them."
Mr Courtney said the employees held hostage during the raid would return to work "once they and their counsellors decide the time is right".
Depot manager Colin Dixon and his wife and young son were kidnapped last Tuesday before the gang of robbers got away with their haul.
On Friday, £1.3m was recovered from a Ford Transit van.