HDB Financial Services, the non-bank lending unit HDFC Bank, said on Tuesday there was a data breach at one of its service providers which processes customer information.
"We have taken immediate steps to secure the service provider's system to prevent any further unauthorized access," HDB said in an emailed statement.
The company did not immediately respond to a Reuters request for comment on the nature of the data breach and how many customers were affected.
HDB is working with a regulator and an office of the government to investigate the incident, it said.
HDFC Bank said it was not affected by the incident.
"We wish to state that there is no data leak at HDFC Bank and our systems have not been breached or accessed in any unauthorised manner. We remain confident of our systems," the bank said in an emailed statement.