After registering the case, the agency carried out searches at the premises of Maran brothers in Delhi and Chennai.
Maxis Communications Berhad (MCB), which has been named in a CBI chargesheet for alleged wrong doing in sale of Aircel, on Tuesday denied charges of using illegal means to acquire the firm from Siva Ventures and said it will pursue all legal remedies to defend itself and its officials.
Former Telecom Minister Dayanidhi Maran, his brother Kalanithi Maran and four others were on Friday chargesheeted by the Enforcement Directorate in the Special 2G court.
They were chargesheeted for alleged offences punishable under section 120-B (criminal conspiracy) of IPC and under relevant provisions of the Prevention of Corruption Act.
The ED had filed the first chargesheet in the case against Chidambaram's son Karti; later, a supplementary chargesheet was also filed against him.
The agency, sources said, has issued the notices under the Prevention of Money Laundering Act (PMLA) and they have summoned the accused to examine them and record their statements.
He was chargesheeted for the offences punishable under section 120-B
On August 29, CBI had filed the charge sheet in the case against Dayanidhi, Kalanithi and six others, including four firms.
Special CBI Judge O P Saini took cognisance of the CBI's charge sheet filed against eight accused including four companies and summoned them on March 2, 2015.
The agency had "almost finished" its probe into the matter, which involved Dravida Munnetra Kazhagam leader and former telecom minister Dayanidhi Maran, an official said.
The CBI had summoned Karti to appear before it on October 4.
If convicted, the offences entail a maximum punishment of seven years.
The ED said that Chidambaram has remained evasive and therefore grant of pre-arrest bail at this stage would be highly detrimental to the investigation.
Former Telecom Minister Dayanidhi Maran had "pressurised" and "forced" Chennai-based telecom promoter C Sivasankaran to sell his stakes in Aircel and two subsidiary firms to Malaysian firm Maxis Group in 2006, the CBI on Thursday told a special court.
The sources said the matter should have been referred to the Cabinet Committee on Economic Affairs as foreign investments above Rs 600 crore (Rs 6 billion) can only be cleared by Cabinet Committee on Economic Affairs headed by the Prime Minister.
The CBI had registered a case against former telecom minister Dayanidhi Maran, his brother MP Kalanithi Maran, Malaysian business tycoon and Maxis owner T Ananda Krishnan, and Maxis Director Ralph Marshall in October 2011.
Chidambaram was competent to give approval of upto Rs 600 crore but he gave the approval which was worth approximately Rs 3,500 crore
In April 2013, CBI had first told the Court there were "some difficulties" in the probe after it went abroad.
Former Telecom Minister Dayanidhi Maran, his brother Kalanidhi Maran and six others, including four companies, were on Friday chargesheeted by the CBI in a special court in the Aircel-Maxis deal case arising out of the investigation in the 2G spectrum allocation scam.