HBO is the focus of a “cyber-incident” reportedly involving hackers leaking forthcoming episodes and scripts of Game of Thrones.

According to Entertainment Weekly, those responsible have already shared data online from other shows as well, including Ballers and Room 104, and have threatened that more is to come.

“HBO recently experienced a cyber-incident, which resulted in the compromise of proprietary information,” a company statement reads. “We immediately began investigating the incident and are working with law enforcement and outside cybersecurity firms. Data protection is a top priority at HBO, and we take seriously our responsibility to protect the data we hold.”

In an email to employees, HBO’s chairman, Richard Piepler, described the attack as “disruptive, unsettling, and disturbing”. The specifics of what hackers have taken have yet to be officially revealed, but the amount of material stolen is believed to total 1.5 terabytes.

Reporters received an anonymous email on Sunday from the hackers that read: “Hi to all mankind. The greatest leak of cyber space era is happening. What’s its name? Oh I forget to tell. Its HBO and Game of Thrones……!!!!!! You are lucky to be the first pioneers to witness and download the leak. Enjoy it & spread the words. Whoever spreads well, we will have an interview with him. HBO is falling.”

The attack is the latest in a line of hacks aimed at major Hollywood companies following Disney being threatened with the early release of Pirates of the Caribbean 5; in April Netflix was targeted with the leak of a new season of Orange Is the New Black.

Game of Thrones remains HBO’s most popular show, with about 10 million viewers having tuned in for the new season’s debut.