The Serious Fraud Investigation Office (SFIO) is probing alleged financial irregularities at debt-laden Aircel as well as two group entities -- Aircel Cellular and Dishnet Wireless, according to a senior official.

The official said the Corporate Affairs Ministry has ordered a probe by the SFIO into the affairs of the three companies.

In February, Aircel announced filing for bankruptcy as the company was been facing "troubled times" in "highly financially stressed" industry.

Intense competition following the disruptive entry of a new player, legal and regulatory challenges, high level of unsustainable debt and increased losses had together caused significant "negative business and reputational impact" on the company, it had said.

The SFIO is a multi-disciplinary organisation, under the ministry, which probes white-collar crimes and frauds that are in violation of Companies Act.

Aircel is already under the lens of the CBI and the Enforcement Directorate. The Aircel-Maxis case pertains to grant of Foreign Investment Promotion Board (FIPB) clearance to firm Global Communication Holding Services in 2006 for investment in Aircel.

With regard to the Aircel-Maxis case, former Finance Minister P Chidambaram and his son Karti Chidambaram are also under the scanner of the two probe agencies.

In March, the Supreme Court had directed the CBI and the ED to complete their probe into the 2G spectrum allocation cases, including the Aircel-Maxis alleged money laundering case, in six months.