Former IRA chief of staff Thomas “Slab” Murphy was tipped off four hours before he was to be targeted in a major cross-border police swoop.

Dawn raids were carried out last week on more than 20 premises as 300 officers from north and south of the border targeted a criminal gang.

Computers, documents and bank statements were seized during the cross-border operation led by the Criminal Assets Bureau.

Operation Loft centered on the activities of a prominent Co. Louth Republican and an organized crime gang who are suspected of laundering and trading illegal fuel.

But Murphy disappeared from his house hours before it was raided.

The Irish Independent reported that detectives discovered evidence that the notorious oil smuggler and his associates knew about the operation and destroyed computers and documents just before the raids took place last Wednesday morning.

Senior security officials are now seriously concerned that the Republican leader has an informant in one of the state agencies investigating him either in the North or the south.

Police Service of Northern Ireland and Garda (Irish police) surveillance officers reported seeing a number of large fires close to the home of Murphy in south Armagh around 2 a.m. The charred remains of laptops, computer disks and documentation were later found in the course of searches by police.

Operation Loft swung into action at 6 a.m. when specialist teams from both police forces surrounded the millionaire’s property.

They were part of a 300-strong force, including police and customs on both sides of the border, who carried out searches across 11 counties.

A large amount of documentation and over €100,000 in cash was seized in the raids at 22 private homes and business premises.

Officers also discovered one of the largest diesel-laundering plants ever found along the border. Sources have revealed that it had the capacity to produce over €5 million worth of illegal fuel a year.

Murphy, 60, is currently charged before the Special Criminal Court in Dublin with nine counts of failing to file income tax returns. He is taking a Supreme Court case to have his trial heard before a judge and jury. He and his family members are also fighting a €5 million tax demand from the Criminal Assets Bureau.

The demand was issued following a similar raid on Murphy’s operation in 2006 when CAB, Customs and the former Assets Recovery Agency in the North uncovered evidence of a hidden economy worth hundreds of millions of euro.

Last week’s raids are not linked to the murder of Detective Garda Adrian Donohoe, who was shot dead near Dundalk in January.

Thomas 'Slab' Murphy narrowly dodges major police raidPA