Peter and Indrani Mukerjea, INX founders, had alleged he had demanded a $1mn (Rs. 6.5cr) bribe for assisting with FIPB clearance.
Officials say he will now be confronted with the Mukerjeas, who are already in jail in a different case.
What is the INX money laundering case?
According to the FIR, INX was approved by the Foreign Investment Promotion Board (FIPB) for investment of Rs. 4.62cr, but actually received Rs. 305cr by sale of shares.
When I-T launched a probe, INX allegedly took the help of Karti's company named Chess Management Services "to get the issues resolved" by influencing FIPB officials.
INX was formerly owned by the Mukerjeas.
Karti has denied any wrongdoing in the FIPB approval
In May'17, ED registered a case against Karti for criminal-conspiracy, cheating, seeking to influence a public servant, and criminal misconduct.
He has "categorically denied" any wrongdoings in the approval, but has been actively detaching himself from suspicious properties and accounts, reports said.
Karti was first grilled by the ED in January. Last week, he had moved the SC seeking a stay on ED's summons.
Karti to be questioned further in Mumbai
On February 28, the CBI arrested Karti from the Chennai airport soon after he landed from London, days after his CA S Bhaskararaman was nabbed.
The next day, a court sent him to custody till March 6.
Today, after landing in Mumbai, he was taken to Byculla prison where Indrani is housed.
Sources say he will be confronted with Indrani and Peter separately.
Mukerjeas in prison for their daughter's murder
The Mukerjeas are in prison in the Sheena Bora murder case. Indrani, her former-husband Sanjeev and her driver Shyamwar Rai allegedly killed her daughter with her first husband, Sheena, as she was dating Rahul, Peter's son from a previous marriage. Peter was arrested for conspiracy.