The Income Tax Department, one of the investigating agencies probing the Satyam fraud case, has asked the Hyderabad Police for documents related to purchases and investments by the firm's former Chairman Ramalinga Raju.

The department has asked the city police to furnish all the related documents that the police had seized and was currently scrutinising them, along with the Serious Fraud Investigations Office (SFIO), an I T Department source said.

The source, however, was unable to specify the period for which the documents had been asked, as they said that since the fraud had happened over several years, "everything and anything would be necessary".

The investigations would take another few weeks and apart from few preliminary dossiers, the final report was still to be prepared and sent to the Central Board of Direct Taxes (CBDT), he said.

Former CBDT Chairman N B Singh, who retired on January 31, had on January 27 said in Mumbai that the department was conducting an independent probe into the Satyam case.

Sources also added that the previous case files pertaining to the returns of Satyam's Hyderabad unit would also form part of their investigation.

I T sources maintained that they were actively coordinating with other probe agencies and certain clues could come out in the next few weeks. Senior officials including Revenue Secretary P V Bhide and CBDT Chairman S S N Moorthy refused to comment on the issue at an Income Tax book launch function in the national capital on Wednesday.

Market regulator SEBI had yesterday secured the Supreme Court's nod to interrogate Satyam Computer founder Ramalinga Raju and his brother Rama Raju for three days beginning tomorrow in connection with the accounting fraud in the firm.