Indian police on Tuesday opened a probe into five coal companies after raiding premises across the country over the alleged misallocation of lucrative mining rights.
Central Bureau of Investigation (CBI) spokeswoman Dharini Mishra said that 30 premises had been visited as detectives examined whether coal companies were guilty of cheating in a scandal that has rocked Prime Minister Manmohan Singh.
"We have registered an FIR (First Information Report) after conducting raids in 10 cities," Mishra told AFP, adding that coal company offices in New Delhi, Mumbai and Kolkata had been targeted.
The FIR, which is a written report representing the first stage of a police enquiry, says the companies are being investigated for cheating and criminal conspiracy.
Mishra declined to name the companies involved but local TV channel NDTV said two of the firms named in the report had links with a Congress parliamentarian from the western state of Maharashtra.
The CBI is set to probe whether some of the firms were set up only to win the coal blocks allocated by the government before selling them on to a third-party at massive profit.
An official auditor's report last month criticised the gifting away of coal blocks, instead of auctioning them to the highest bidder, and said the process of selecting companies "lacked transparency and objectivity".
Private operators who won coal blocks without competition enjoyed "financial gains to the tune of 1.86 trillion rupees ($33.4 billion)" since 2004, some of which should have gone to the government, the auditor claimed.
Singh's coalition government, led by the left-leaning Congress party, has been beset by a string of corruption cases since re-election in 2009 and the latest allegations of mismanagement have led to renewed pressure on him.
The coal scandal implicates the 79-year-old directly because he served as coal minister as well as prime minister from 2004-2009.
The Hindu nationalist Bharatiya Janata Party (BJP) and other opposition parties have forced parliament to be adjourned daily over the issue and have demanded the prime minister's resignation.
The BJP welcomed Tuesday's raids while insisting that allocations of all the coal blocks should be cancelled immediately.
"It is a good development. Taking a cue from this, the government should also cancel the coal block allocations," BJP leader Gopinath Munde told reporters after a meeting of the party's top brass in New Delhi.
Singh has strongly rejected charges over the coal scandal, saying the auditor's findings were not supported by facts.
His office refused to comment on the latest development, but the coal minister said the move by the CBI should put an end to speculation over the impartiality of the probe.
"Those who allege CBI works on government instructions, they should answer now how they feel about the CBI action," said Jaiswal.