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 good the devices are at keeping secrets.

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