Thousands of depositors are said to have been duped in alleged scam.
The Enforcement Directorate (ED) has also summoned Karnataka Food and Civil Supplies and Wakf Department Minister B Z Zameer Ahmed Khan for questioning in the case on 5 July, officials said.
The central agency said its Bengaluru zonal office has issued a provisional order under the Prevention of Money Laundering Act (PMLA) for attachment of immovable assets worth ₹197 crore and about ₹12 crore deposits in bank accounts.
While the minister has denied any business dealings with the group or its absconding main promoter Mohammed Mansoor Khan, except sale of a Bengaluru-based property, the agency wants to question Zameer Khan about his links with the company and its operations, they said.
Zameer Khan said ED officials have served him a notice to furnish details about the sale of the property. "Yes, the ED officers have issued summons.They have asked me to furnish details. Two people had come, " he said.
"They have asked me to furnish details by 5 July regarding the property I had sold (to Mansoor). I will give the details," the minister said.
The ED had recently filed a criminal case of money laundering against the IMA group of companies and Mansoor Khan (also the managing director of the group) after reports emerged that he has gone underground fearing investments worth crores of about 40,000 investors have tanked.
While ₹98 lakh was found deposited in 51 bank accounts, ₹11 crore was kept in a HDFC bank account, operational under the Pradhan Mantri Garib Kalyan Yojna (PMGKY), the ED said.
The PMGKY was announced by the Modi government, post demonetisation in 2016, as part of a one-time compliance window for people holding black money to come clean by paying tax and penalty of 50 per cent. The government had said such declarations will be kept confidential.
The ED said Mansoor Khan had deposited cash of about ₹44 crore in various bank accounts during the demonetisation period and as a result of Income Tax Department action against the IMA group, he and the IMA group had paid a tax of ₹22 crore.
"The remaining amount of ₹11 crore was lying in a bank which has been identified during the investigation," it said.
In a statement, the agency said the value of the 20 immovable properties attached as per the latest order is about ₹197 crore and their worth has been obtained by approved government valuers.
This way, the total amount of the attachment is about ₹209 crore.
The immovable assets which have been frozen include those located in Jayanagar, Alexanderia Street, Frazer Town, Serpentine Street, Tasker Town, Pottery Town, HBR Layout, Benson Town, Davis Road, Richards Town, St Johns Church Road, Maruthi Sevanagar and Bannerghatta in Bengaluru.
Two properties at Lady Curzon Road, five acres of land and a plot in Davangere, two properties in Hassan and one asset in Chikkaballapur have also been frozen.
The ED said it has deployed a "dedicated" team of investigators to probe the case and that Mansoor Khan had received about ₹4,000 crore as investments from the gullible investors.
The "accused companies and its directors have indulged in the offence of money laundering by cheating common people through ponzi schemes and generated the proceeds of crime in the form of movable and immovable properties", it said.
Probe revealed that the IMA group was "not doing any business to pay the promised monthly return on the investments made by public and Khan was running a ponzi scheme and they (group employees and directors) were all working on the instructions of Mansoor Khan", the ED alleged.
Mansoor Khan, it said, had promised returns ranging from 2.5 to 3 per cent month to the investors, who are mainly from the Muslim community. The scam had come to light after a video of his purported statement claiming that the investments have been lost, surfaced early this month.
The ED has summoned Khan multiple times for questioning but he did not depose before the agency and it is suspected that he has left the country.
The agency is working towards getting an Interpol arrest warrant issued against him and get him declared a fugitive economic offender by a court, it said.
The Karnataka government has constituted a special investigation team (SIT) of the police to probe the case, which has already arrested seven directors of the group.
The BJP's Karnataka unit recently demanded a CBI probe into the alleged fraud and also raised questions about Zameer Khan's alleged links with Mansoor Khan.
"While asking him (Mansoor) to come back, Zameer, who is a minister, has said that 'the government is with you (Mansoor), don't fear'. What does this mean? The chief minister has to answer," state BJP chief B S Yeddyurappa had said.
Hitting back at Yeddyurappa, Zameer Khan had said it was he who took the initiative after the incident came to light and sought a probe by a Special Investigation Team.
This story has been published from a wire agency feed without modifications to the text. Only the headline has been changed.