The Assets Recovery Agency (ARA) searched several properties in Manchester on Thursday; an investigation local media said was part of a probe into Irish Republican Army activities.
The agency said in a statement it had so far uncovered a portfolio comprising 250 properties worth a total of 30 million pounds held by two men.
The agency declined to give details of the identity of the men and would not comment on reports it was linked to the IRA.
"The searches were carried out on domestic and business properties associated with two Manchester-based businessmen," the statement said.
The ARA said it had identified around 250 properties held by both of the businessmen and a number of property management companies.
"The equity in the properties appears to be in the region of 9 million pounds," it added, reports Reuters.
According to Guardian, a British detective, speaking to The Associated Press on condition of anonymity because of the sensitivity of the investigation, said several months of digging into Murphy's dealings had led them to Craven. He said Murphy was suspected of buying dozens of properties through intermediaries since 2002.
The detective said tracing Murphy's holdings was difficult because of the fuel dealer's insistence on all-cash transactions involving friendly business intermediaries and no bank accounts. He said Murphy's name was not on any of the properties investigated.
Murphy has never given an interview and has rarely been photographed. An AP reporter who tried to visit his farm which lies half in County Louth in the Republic of Ireland, half in Northern Ireland was prevented by an unidentified young man from doing so.
Murphy came into the public domain in 1985 when a British newspaper, The Sunday Times, published a major expose. Murphy sued for libel but lost twice, most recently in 1998, when a Dublin jury ruled Murphy was an IRA commander and border smuggler.