The Federal Bureau of Investigation was unable to access data from nearly 7,800 devices in the fiscal year that ended Sept. 30 with technical tools despite possessing proper legal authority to pry them open, a growing figure that impacts every area of the agency's work, Wray said during a speech at a cyber security conference in New York.

The FBI has been unable to access data in more than half of the devices that it tried to unlock due to encryption, Wray added.

"This is an urgent public safety issue," Wray added, while saying that a solution is "not so clear cut."

Technology companies and many digital security experts have said that the FBI's attempts to require that devices allow investigators a way to access a criminal suspect's cellphone would harm internet security and empower malicious hackers. U.S. lawmakers, meanwhile, have expressed little interest in pursuing legislation to require companies to create products whose contents are accessible to authorities who obtain a warrant.