At the same time the FBI was struggling to unlock the iPhone of San Bernardino terrorist Syed Farook, the agency was being inundated with requests from state and local law enforcement seeking help accessing the contents of hundreds of encrypted or damaged cellphones linked to unrelated criminal investigations scattered across the country, reports USA Today.

Requests involving more than 500 such devices streamed into the bureau’s Computer Analysis Response Team and the agency’s Regional Computer Forensic Laboratory programs during a four-month period beginning last October, two months before agents seized Farook’s device in the aftermath of the mass shooting that left 14 dead, according to the FBI.

The numbers, the most recent accounting provided by the agency, offer an assessment —albeit limited — of the mounting investigatory challenges posed by encryption and other technological hurdles beyond the San Bernardino case that launched the government’s recently aborted court battle with Apple Inc.

Recently, a separate survey of more than a dozen state and local law enforcement agencies, based on data gathered by the Manhattan District Attorney's Office and USA TODAY, found that investigators have been blocked from the contents of more than 1,000 smartphones and other devices in recent months.

Many of the devices, manufactured by Apple and other makers, sit in the archives of evidence rooms where authorities were forced to resolve cases without the information contained in the blocked devices. Still other devices are linked to open investigations ranging from shootings and kidnappings to white-collar inquiries.

The FBI, which abruptly withdrew from its legal battle to force Apple's assistance in unlocking the Farook phone after getting the help of an undisclosed "outside party,'' said in a statement Wednesday that the mass of recent requests for forensic help have involved efforts to retrieve deleted data, salvage damaged hardware, access encrypted content and bypass locked phones. In the Farook case, investigators had sought Apple's help in bypassing the security function to unlock the device.

"Please know that we will continue to do everything we can to help you consistent with our legal and policy constraints,'' the FBI told local law enforcement agencies. "You have our commitment that we will maintain an open dialogue. We are in this together."