Malaysia’s Malindo Air, a subsidiary of Indonesia’s Lion Group, said on Wednesday it was investigating a data breach involving the personal details of its passengers.

Malindo Air’s statement followed a report by Moscow-based cybersecurity firm Kaspersky Lab that the details of around 30 million passengers of Malindo and fellow Lion Group subsidiary Thai Lion Air were posted in online forums. The report said the leaked information included passengers’ passport details, addresses and phone numbers.

Lion Group and Thai Lion Air could not immediately be reached for comment.