Two people held by police investigating the £26.5m Northern Bank robbery in Belfast are understood to be employees.
Chris Ward was interviewed on BBC's Spotlight programme
A 24-year-old man and a 22-year-old woman were arrested early on Tuesday at different addresses.
It is understood Northern Bank employee Chris Ward is one of the two people detained in the latest arrests over the December 2004 raid.
After the bank robbery, Chris Ward described how he had been held captive in the run-up to the raid.
The details were given in an interview with BBC's Spotlight programme.
He described in detail how he and a male colleague were forced to facilitate the theft of millions of pounds from the cash centre of the Northern Bank's headquarters.
Police Land Rovers have been at the Ward family home in the Poleglass area of west Belfast since about 0600 GMT.
PSNI Land Rovers outside the Ward family home
Earlier this month, police investigating the robbery arrested several people.
Of the 10 people questioned to date in connection with the robbery, three have already appeared in court.
The robbery happened at the bank's Northern Ireland headquarters at Donegall Square West just before Christmas last year.
Some money seized in County Cork last February was linked to the robbery, but virtually all of the missing millions remain unrecovered.
Chief Constable Sir Hugh Orde subsequently blamed the IRA for the raid.