South Korea's Financial Supervisory Service is starting an on-site inspection of Yegaram Savings Bank, where a hacking incident led to the leak of customers' personal information.

Financial authorities said on Tuesday that the watchdog will visit Yegaram Savings Bank that day to check the cause of the hacking incident and how personal information was leaked.

Yegaram Savings Bank confirmed on Sept. 30 indications that customer personal information was leaked after an external hacker gained access to its server. The scale of the leak is estimated at about 50,000 cases. It was found to include names and contact details, as well as resident registration numbers, account numbers and addresses.

In particular, in its first notice on Oct. 2 it said only names, dates of birth and contact details had been leaked, but later added resident registration numbers and account numbers.

Yegaram Savings Bank said it suspended related services immediately after becoming aware of the incident and took emergency steps, including blocking external IP addresses and strengthening security monitoring.

The Financial Supervisory Service plans to decide whether to switch to a formal inspection based on the on-site inspection results.