Two Northern Ireland bank employees were arrested Tuesday on suspicion of involvement in the $50 million robbery of their Belfast bank, raising questions about whether the theft, a British record, could have been an inside job.

Chris Ward, 24, and a 22-year-old woman whom police would not identify were being held at a police interrogation center in Antrim, west of Belfast. Under anti-terrorism laws, they could be held there for up to a week before being charged or released.

A detective familiar with the investigation into the Dec. 20, 2004, robbery confirmed that Ward and a female friend of his were under arrest. The detective spoke on condition of anonymity because it is against police policy to discuss the identities of suspects before they are charged.

Four armored police vehicles were parked outside Ward's home in Poleglass on the outskirts of Catholic West Belfast, a power base of the outlawed Irish Republican Army. Forensic specialists in protective clothing searched both the house and a car outside.

Northern Ireland police commanders, the British and Irish governments, and international experts all have accused the IRA of robbing the central vault of the Northern Bank. The IRA has denied involvement.

Masked, armed gangs took Ward and his family hostage, along with the family of another bank employee, and threatened to kill them unless both employees cooperated and raised no alarms.

In an interview with the BBC days after the robbery, Ward stressed he had played no role and was an innocent victim. He said a man who was covering his face with a hat and coat collar arrived at his family's Poleglass home on the night of Dec. 19, then pulled a gun, donned a balaclava-style mask and brought in more henchmen, who held Ward's family captive for the following 24 hours until the robbery was over.

Ward said the gang leader warned him that if he disobeyed orders, "You and your family are dead."

Ward said he was taken to the rural home of his co-worker, Kevin McMullan, where a second gang was holding McMullan and his wife. Ward said he and McMullan both were ordered to go to work, stay past closing time, then ferry boxes of cash to a waiting van.

"It was very difficult to do, but you knew in the back of your head that you had to do it, that you couldn't tell anybody," Ward told the BBC.

Three people have been charged and ordered held without bail in connection with the robbery investigation. None has been accused of actually carrying out the raid.

Hugh Orde, commander of Northern Ireland's police, has said detectives have accounted for $9.5 million of the stolen cash.

Police in neighboring Ireland seized about three-fifths of that total during raids in February on the homes and offices of people suspected of laundering money for the IRA.

The remaining two-fifths, police estimate, was burned before it could be seized during those raids.

Orde said the bulk of the missing money has been rendered worthless because the Northern Bank -- which is allowed to print and distribute its own designs of British currency -- withdrew its previous designs from circulation and issued new notes.