New Delhi, April 26:  The CBI has registered a case against former Aircel promoter C Sivasankaran's companies, Axcel Sunshine Ltd and Finland-based Win Wind Oy, for allegedly defaulting on loans worth Rs 600 crore taken from IDBI bank, officials said today.

They said the agency is carrying out searches at 50 locations, including the residences of former senior IDBI bank officials. The searches are spread across Delhi, Mumbai, Faridabad, Gandhinagar, Chennai, Bangalore, Belgaum, Hyderabad, Jaipur and Pune, the officials said.

Sivasankaran allegedly took a loan of Rs 530 crore in February 2014. This swelled to Rs 600 crore after becoming NPA, they said.

The case has been registered under sections relating to criminal conspiracy, cheating and corruption against British Virgin Islands based Axcel Sunshine Limited on allegations of perpetrating fraud through the loan accounts of Win Wind Oy, Finland and Axcel Sunshine Limited, the officials said.