HBO has had some of its programming stolen in what is being described as a cyber incident.
The company says that it is working with law enforcement and cybersecurity firms.
HBO CEO Richard Pepler says in an email to the network's employees that "proprietary information" was stolen in the hack. Spokesman Jeff Cusson would not comment on which specific TV episodes, movies or other video the hackers made off with.
Hacking Hollywood can have significant repercussions. Sony struggled in the aftermath of its huge hack in 2014, which leaked employee emails as well as films.
In April, a hacker claimed to have released episodes of Netflix's "Orange is the New Black" before their release by the streaming site.