Belfast, Northern Ireland ? The Irish Republican Army stole $50 million from a Belfast bank, the Northern Ireland police chief bluntly declared Friday — an announcement that rocked the foundations of the peace process.

The British and Irish governments accepted Chief Constable Hugh Orde’s verdict and said the development had gravely undermined years of effort to revive a Catholic-Protestant administration involving Sinn Fein, the IRA-linked party.

Power-sharing was the central goal of the Good Friday peace accord of 1998. A previous coalition involving Sinn Fein collapsed in 2002 because of arguments over IRA activities, and since then, negotiators have been striving in vain to secure the outlawed group’s disarmament and disbandment.

The Dec. 20 raid on the Northern Bank, when a gang held the families of two employees hostage until the bank’s main vault was cleared out, was the biggest cash robbery in history. It came a week after months of negotiations narrowly failed to reach a new power-sharing deal between Sinn Fein, which represents most of the province’s Irish Catholics, and the Democratic Unionists, the party backed by most British Protestants.

Paul Bew, politics professor at Queen’s University of Belfast, said growing optimism that the opposing forces could form a coalition suddenly seems “a very dreamy, utopian concept.”

“The politics have grown very dark here. We are in a genuinely unexpected situation,” he said.

A 45-member detective team trying to catch the thieves has searched more than a dozen properties in IRA strongholds of Belfast but made no arrests.

Orde — who previously refused to comment on the case — said he couldn’t reveal any evidence that the IRA was responsible because it could jeopardize the investigation or potential intelligence sources close to the IRA, which has a policy of killing informers.

The Northern Bank, meanwhile, announced an unprecedented plan to make most of the robbers’ bounty useless.

Chief Executive Don Price said the bank would withdraw from circulation all Northern Bank-produced currency, a process that could take weeks and cost the bank up to $9.5 million. About three-fourths of the stolen British pounds bore Northern’s name and design.

Withdrawing the currency, Orde said, would transform the robbery into “the largest theft of waste paper in the living history of Northern Ireland. The money will not be worth anything as soon as that takes place.”