That's according to six sources Reuters spoke to.

Under the original plan, Apple would no longer have a key to unlock the encrypted data, meaning it would not be able to turn material over to authorities in a readable form even under court order.

But a year after Apple informed the FBI of the plan, the company reversed course. Though Reuters could not determine why exactly Apple dropped the plan.

The move shows how much Apple has been willing to help U.S. law enforcement and intelligence agencies, despite taking a harder line in high-profile disputes with the government.

Last week, Attorney General William Barr took the rare step of calling on Apple to unlock two iPhones used by a Saudi Air Force officer who shot dead three Americans at a Pensacola, Florida naval base last month.

Apple did in fact did turn over the shooter's iCloud backups in the Pensacola case, and said it rejected the characterization that it "has not provided substantive assistance."