NEW DELHI: Federal law enforcement officials raided offices and homes in 10 cities across India on Tuesday as part of an investigation into irregularities in the award of coalfield concessions to private and state companies that has sparked a political crisis.

The Central Bureau of Investigation (CBI) has filed cases against five companies and charged a number of officials with criminal conspiracy, cheating and intention to commit a crime, CBI officials said. No arrests have yet been made, although documents have been seized.

The five companies, which are not listed on stock exchanges, are small-time players in the main coal-producing states of eastern India. They include Vinni Iron & Steel, JLD Yavatmal Energy, Jas Infrastructure and AMR Iron & Steel, a CBI official said on condition of anonymity because raids were still under way.

Jas Infrastructure confirmed there had been a raid on its corporate office, but there was no immediate confirmation from other companies.

The raids come at a critical time for Prime Minister Manmohan Singh's government, which has been on the defensive since the state auditor last month questioned the lack of transparency in the allocation of scores of coalfields.

The main opposition Bharatiya Janata Party (BJP) seized on the report to paint the government as corrupt and has all but paralysed parliament with its demands for Singh to quit over the affair, which the Indian media has dubbed “coalgate”.

The CBI launched an inquiry into allegations of irregularities in the allocation process before the auditor released his report on Aug 17, but the raids widen the furore beyond parliament, where it has been playing out for weeks.

The report questioned the lack of competitive bidding for coalfields potentially worth billions of dollars but did not accuse Singh or other officials of corruption.

Singh has denied any wrongdoing in the allocation of 142 coalfields by a government panel between 2004 and 2009.

Indian media have reported that some of the companies that won concessions misrepresented their ability to mine the coal or were linked to political parties.