Rangers were shocked to find officers from Strathclyde Police arriving at Ibrox Stadium yesterday before 8am as part of the fraud operation involving three British clubs.

Officers spent an unspecified time inside Ibrox, with Rangers later acknowledging in a statement that they had cooperated with the police.

It was the second time inside two months that Rangers found themselves named in a fraud investigation. After the recent publication of the Stevens report, in which the transfer of Jean Alain Boumsong from Rangers to Newcastle United in January 2005 was said to require further scrutiny because of irregularities, yesterday’s development caused further discomfort for the Ibrox club.

It remains unclear whether the Boumsong transaction was a specific part of the police activity yesterday, with sources claiming that this latest development was not strictly related to the findings of Lord Stevens of Kirkwhelpington and the Quest team.

The Boumsong transfer, however, appears to be the only business connecting Rangers to Newcastle in recent seasons and has remained the subject of some intrigue. The France defender was signed by Rangers on a Bosman free transfer from Auxerre, but left six months later for a reputed £8 million when signed by Graeme Souness, the Newcastle manager at the time.

Martin Bain, Rangers’ chief executive who was director of football operations at the time, conducted the Boumsong business on behalf of Rangers. The agent involved was believed to be Willie McKay, who is based in Monaco.

The police investigation is a setback for Rangers, with the club trying to generate fresh optimism among supporters under their new manager, Walter Smith, after two trophy-less seasons. In recent years the club have successfully wiped out an onerous £80 million-plus debt, but there has been continuing speculation about the future commitment to the club of Sir David Murray, the Rangers chairman for the past 20 years.

Murray is believed by various figures close to Rangers to be actively seeking a buyer for his 90 per cent stake in the club. After years of heavy investment, Rangers have been significantly outspent by Celtic over the summer, leading to further agitation among sections of the club’s support.

Murray, Bain and those supporters will all be hoping that yesterday’s police activities provide no further headaches for the club.