South Korean authorities are investigating the theft of over $30 million from a Seoul-based cryptocurrency exchange, which experts say resembles an attack by North Korea’s Lazarus Group on the same company six years ago.

Unnamed sources in South Korea’s information and communications technology industry and government said Friday that authorities are conducting an on-site inspection of the hacked exchange Upbit and “strongly suspect” Pyongyang is behind the heist, Yonhap News Agency reported.