Serious Fraud Officers and police have raided six homes and an office over allegations involving claims for miners' compensation.
The miners' fund is the world's largest personal injury scheme
Files and computer records were taken for analysis but no arrests were made.
The raids in Mansfield, Nottinghamshire were part of an on-going police inquiry into compensation claims made on behalf of former miners.
The fraud officers are looking at the activities of Indiclaim Ltd, also known as Walker & Co (Claims Services) Ltd.
South Yorkshire Police announced in June that they are looking into claims that funds from a compensation scheme set up by the government were misappropriated.
The Nottinghamshire-based Union of Democratic Mineworkers and a number of solicitors' firms have been processing claims on behalf of tens of thousands of ex-miners or their families in what has become the world's biggest personal injury compensation scheme.
The £7.5bn compensation scheme was set up by the government in 1999 and has been paying out to tens of thousands of miners suffering from chronic lung disease and vibration white finger.