NEW YORK — Police and prosecutors in New York City said Thursday that the top-notch encryption technology on Apple mobile phones is now routinely hindering criminal investigations.

And they predicted the problem could grow worse as more criminals figure out how well the devices keep secrets.

Manhattan District Attorney Cyrus R. Vance Jr. said at a news conference that investigators cannot access 175 Apple devices sitting in his cybercrime lab because of encryption embedded in the company’s latest operating systems.

“They’re warrant proof,” he said, adding that the inability to peer inside the devices was especially problematic because so much evidence once stored in file cabinets, on paper, and in vaults, is now only on criminals’ smartphones.

Apple has marketed its encryption data as an important privacy tool, and many privacy advocates have praised the company, saying that if it opened its devices to government surveillance that ability to spy on users could be abused in places with authoritarian regimes.

The Cupertino, California-based company is currently fighting a federal magistrate’s order to help the FBI hack into an iPhone used by a gunman in December’s mass shooting in San Bernardino, California.

Vance didn’t specify which cases were being hindered.

But Police Commissioner William Bratton said a phone seized in the investigation of the shooting of two police officers in the Bronx last month is among those detectives can’t crack. It was displayed Thursday alongside other phones, iPads and tablets similar to 600 devices the prosecutor’s team tested, of which the 175 proved inaccessible.

Bratton said criminals are increasingly aware of the protection offered by their devices. He said a prisoner in a city jail was recently recorded saying in a phone call that iPhone encryption was “another gift from God.”

Vance said investigators have relied on phone data to investigate killings, child pornography, robbery and identity theft. He said that might include checking a suspect’s contact list to get the names of witnesses or conspirators, or viewing incriminating videos and photographs.

Apple CEO Tim Cook has warned that creating software allowing the FBI to unlock the San Bernardino suspect’s phone could make millions of other phones vulnerable to hackers and criminals.

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