New Delhi (Agencies): Indian industrialist Anil Ambani's Reliance ADA Group, which runs No. 2 mobile carrier Reliance Communications, said authorities had "examined" some of its officials and that it was cooperating.

The Central Bureau of Investigation (CBI) has been looking into probable indiscretions in the allocation of telecommunications licences and radio airwaves after a state auditor said licences were sold too cheaply in 2007-08, at a cost to the government of up to $39 billion in potential revenue.

The telecoms licensing scandal is one of numerous that has tainted the government of Prime Minister Manmohan Singh, led to a near-shutdown of parliament and rattled investors.

The Supreme Court had directed the CBI to investigate licence grants starting from 2001.

"The CBI is reportedly examining a large number of telecom companies and their officials over the past several weeks, in relation to various matters relating to the years 2001 to 2008," a spokesperson said.

"As part of this process, CBI has also examined a few officials of Reliance ADA Group, and we are fully co-operating with the authorities in this regard," the statement stated.

Reliance Communications, predominantly a CDMA carrier, was granted rights to spread its GSM services in 2007.

In a report released in November, a government auditor said Swan Telecom, which was later renamed Etisalat DB, was awarded a licence even though a unit of Reliance Communications held more than 10 per cent of equity in the company, a violation of norms.

Reliance Communications has claimed the group did not have any shareholding in Swan when licences were given in January 2008.

Reliance ADA Group firms including Reliance Communications this week saw their share prices fall stridently, which the group blamed on rivals for spreading what it said were "baseless" rumours.