The United Kingdom's anti-racketeering agency affirmed it has searched 250 properties in northwest England and one investigator said it was a probe into the finances of a reputed Irish Republic Army leader.
The Assets Recovery Agency, acting on search and seizure warrants, released no information about the targets of the investigation.
However, a Belfast-based investigator involved in the probe, who spoke on condition of anonymity because of the sensitivity of the case, said the action was part of a probe into reputed IRA leader Thomas "Slab" Murphy's finances.
The agency said it had identified a portfolio of 250 properties in Manchester believed to be worth about 30 million pounds.
"The searches were carried out on domestic and business properties associated with two Manchester-based businessmen," the agency said in a statement.
Gerry Adams, leader of the IRA-linked Sinn Fein party, told reporters in London that leaks about the investigation were politically motivated.
"I don't think it's any accident, I'm not surprised that this is trotted out today. It's obviously a political agenda," Adams said before a meeting with Prime Minister Tony Blair.
The Assets Recovery Agency is based in London and it also has an office in Northern Ireland. It is designed to disrupt organized crime networks by recovering criminal assets.
In recent years, the British and Irish governments have formed special anti-racketeering units armed with new powers to seize the assets of well-known criminals - even those who have never been convicted of a major crime.
U.K. and Irish anti-terrorist police identify Murphy as the IRA's chief of staff, the senior figure responsible for daily operations. Several books on the IRA also identify Murphy as holding this position, the AP reports.
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