Facebook Inc. (FB.O) is suing BlackBerry Ltd. (BB.TO) for patent infringement, escalating the legal battle between the two companies over protected technology.

In a 118-page complaint filed filed Tuesday in San Francisco federal court, Facebook accused BlackBerry of stealing its voice messaging technology, among other patented processes. Facebook is seeking unspecified damages.

In March, BlackBerry sued Facebook in federal court in Los Angeles, accusing the social media giant of infringing on its mobile messaging patents.

BlackBerry claimed Facebook made unauthorized use of its technology in its own instant messenger service, Facebook Messenger, and in WhatsApp Messenger and Instagram.

BlackBerry Seeks New Life From Old Patents to Stem Sales Decline

The case is Facebook v. BlackBerry, U.S. District Court, Northern District of California (San Francisco).