British authorities have begun searching 250 properties in the northern city of Manchester valued at $55 million in what British and Irish news reports said was an investigation linked to the Irish Republican Army.

Police officers and officials of the Assets Recovery Agency, which investigates financial proceeds of crime, raided numerous houses and businesses "associated with two Manchester-based businessmen," the agency said in a statement. It said warrants were issued for the searches but did not identify the businessmen or provide any other details.

News reports said the investigation centered on Thomas "Slab" Murphy, reputed to be a senior official in the IRA, who has a farm that straddles the border between Ireland and Northern Ireland.

In 1998 Murphy sued the Sunday Times newspaper in London for naming him as a top IRA commander, but a Dublin jury found for the newspaper.

Investigators have long said that some IRA leaders have enriched themselves by engaging in cross-border smuggling, extortion and other illegal activities. Police in Northern Ireland have said the IRA was responsible for a Belfast bank robbery last year in which about $50 million was stolen.

Officials at the Belfast office of Sinn Fein, the political wing of the IRA, had no comment on Murphy or the Manchester searches.

Television footage on the BBC and other media outlets showed police guarding the Manchester offices of the Craven Group, which the BBC said was run by Dermot Craven, a local businessman. It said Craven's home had also been searched. It was unclear Thursday what relationship, if any, there was between Craven and Murphy.

The government action came 11 days after independent monitors certified that the IRA had scrapped its vast stockpile of weapons, effectively ending its 36-year armed guerrilla campaign.

Sinn Fein's leader, Gerry Adams, visited British Prime Minister Tony Blair at his 10 Downing Street offices Thursday shortly after a visit by Ian Paisley, the hard-line leader of Northern Ireland's largest Protestant political party. Paisley has expressed doubts that the IRA has disarmed and anger at Blair's government for believing it.

Officials searched the Manchester home of businessman Dermot Craven in an inquiry that news reports said was linked to the Irish Republican Army.