They are being questioned about their business dealings with Videocon Chairman Venugopal Dhoot and about the financial transactions that took place between them, said an ED official.
The case is related to the alleged irregularities and corrupt practices in the sanction of a Rs 1,875-crore loan disbursed by ICICI Bank to the Videocon Group between 2009 and 2011.
The ED alleges that while heading ICICI Bank, Chanda Kochhar illegally routed crores of rupees to NuPower Renewables Ltd, a company run by her husband.
The Kochhars were questioned on many occasions last month in Mumbai. They are being questioned in Delhi for the first time. The couple has been facing over eight to nine hours questioning every day since May 13.
In March, the ED had searched the residence and office premises of Kochhars and also questioned them along with Dhoot.
Dhoot allegedly invested in NuPower Renewables Ltd through his firm Supreme Energy as quid pro quo for the loans cleared by the ICICI Bank.
A large portion of the Rs 40,000 crore loan to the Videocon group remained unpaid at the end of 2017, and the bank proceeded to declare Rs 2,810 crore of this loan as non-performing asset (NPA).