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PHILADELPHIA (AP) – FBI Director Christopher Wray says federal agents haven’t been able to retrieve data from more than half of the mobile devices they’ve tried to access in a year.

Wray spoke Sunday at the International Association of Chiefs of Police conference in Philadelphia.

He says the FBI hasn’t been able to access more than 6,900 mobile devices in 11 months.

Law enforcement officials have long complained about being unable to unlock and recover evidence from cellphones seized from suspects even if they have a warrant. Technology companies have insisted they must protect customers’ digital privacy

Wray called it a “huge problem” and says there needs to be a balance between encryption and public safety.

He also touted partnerships with local and federal law enforcement officials to combat counterterrorism and violent crime.

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