The Irish Republican Army (search) committed last month's massive robbery of a Belfast bank, the Northern Ireland police commander bluntly announced Friday in a move that complicated the province's peacemaking efforts.

Chief Constable Hugh Orde said his detectives probing the Dec. 20 theft at Northern Bank (search) — when a hostage-taking gang stole an estimated $50 million, the biggest all-cash robbery in history — were confident that members of the outlawed IRA planned it and carried it out.

"We are confident this crime was committed by the Provisional IRA," Orde said, using the group's full formal name.

"I would not have made that statement without having spent a great deal of time speaking to my senior detectives and my senior analysts," added Orde.

He declined to specify any evidence pointing to IRA involvement, saying this would compromise his detectives' work. No arrests have been made.

The IRA and its allied Sinn Fein (search) party repeatedly have rejected mounting accusations of IRA involvement in the robbery. Speaking shortly before Orde, Sinn Fein deputy leader Martin McGuinness (search) — a reputed IRA commander since the mid-1970s — said the IRA had told him it wasn't involved.

Previously, leaders of the 45-member detective team hunting the robbers had identified the IRA as one of five possible criminal gangs responsible. Orde's unambiguous declaration, pinning responsibility solely to the IRA, caught many political observers off guard.

Protestant leaders said the verdict from Orde — who had previously avoided any public comment on the case — would harden their opposition to forming any new power-sharing administration with Sinn Fein, the major Catholic-backed party.

The robbery immediately followed the conclusion of several months of negotiations that tried to revive power-sharing, the central goal of the 1998 peace accord for Northern Ireland. The question of whether the IRA would disarm publicly and disband hobbled the effort.

Ian Paisley Jr. (search), a negotiator for the major Protestant-backed party, the Democratic Unionists, accused Sinn Fein leaders of having a hand in plotting the robbery.

"The process is over for Sinn Fein and we must move on without them," said Paisley, whose party would prefer to forge a cross-community coalition with moderate Catholic leaders.

Referring to Sinn Fein, he said, "How can we have a government with people who say `we want a new mode IRA' when the IRA is recruiting and has more resources than ever before?"

Orde, meanwhile, confirmed the Northern Bank would withdraw all of its newly minted currency from circulation.

He confirmed that the gang stole 26.5 million pounds ($50 million), not 22 million pounds ($42 million) as was previously estimated. He said about three-fourths of the stolen money was Northern Bank-branded currency.

Orde said Northern Bank executives "intend to withdraw all their banknotes from circulation and to reissue them in a new color and style."

"The money will not be worth anything as soon as that takes place," he said.