The FBI may have found a way without Apple’s assistance to unlock the iPhone used by one of the shooters in the San Bernardino terrorist attack, Justice Department officials said Monday.

Less than 24 hours before a highly anticipated hearing over access to the phone was set to begin, Justice Department lawyers requested a delay. A federal judge here agreed to postpone the oral arguments in which Apple and the U.S. government were set to face off over whether a court could force Apple to help the FBI unlock the phone.

The sudden about-face was a stunning development in a month-long legal saga, as government lawyers and the FBI director had been insisting for the past month that the bureau had found no other way to obtain access to the locked phone than to compel Apple to assist the government.

[Johns Hopkins researchers poke a hole in Apple’s encryption]

“Our top priority has always been gaining access into the phone used by the terrorist in San Bernardino,” Justice Department spokeswoman Melanie Newman said. “With this goal in mind, the FBI has continued in its efforts to gain access to the phone without Apple’s assistance, even during a month-long period of litigation with the company.”

On Mar. 10, the Department of Justice filed a response to Apple's motion opposing a court order to help the FBI unlock San Bernardino shooter's iPhone. Here are the latest facts we know about Apple vs. the FBI. (Jhaan Elker/The Washington Post)

On Sunday, the U.S. attorney in Los Angeles, Eileen Decker, said in a terse application to a magistrate judge in Riverside, Calif., that “an outside party demonstrated to the FBI a possible method” to unlock the phone used by Syed Rizwan Farouk.

Farouk and his wife were killed in a shootout with police after the Dec. 2 attack, which claimed 14 lives.

If the method works, Decker said, it should eliminate the need for help from Apple.

It could also raise questions about the FBI’s capabilities in unlocking digital devices. “This suggests that the FBI either doesn’t understand the technology well enough or wasn’t telling us the full truth earlier when it said that only Apple could break into the phone,” said Alex Abdo, an attorney with the American Civil Liberties Union, which filed an amicus brief on behalf of Apple in the case.

A senior law enforcement official took issue with that statement and said that the great publicity surrounding the case prompted more companies to come forward with potential solutions.

Newman stressed that the bureau must first test the method to ensure it doesn’t destroy the data on the phone. “We remain cautiously optimistic,” she said. “If this solution works, it will allow us to search the phone and continue our investigation into the terrorist attack that killed 14 people and wounded 22 people.”

Magistrate Judge Sheri Pym directed the government to report back by April 5.

Though the case centers on one iPhone, it potentially has much larger implications for privacy and national security. If the legal battle resumes, it almost certainly would drag on for months, potentially up to the Supreme Court.

Last month, the Justice Department announced it had obtained a court order under the All Writs Act to force Apple to create software to disable a phone security feature so that the FBI could try its hand at unlocking the device by cracking a numeric password.

Apple argued that the law the government cites does not permit a court to force it to do such a thing, that doing so would violate its constitutional rights, and that a ruling in the government’s favor would set a precedent that could weaken overall device security and privacy for users around the world.

The government argued that the law did authorize the court to direct Apple to provide the assistance and that Apple, which creates its own software, was the only party that was in a position to help.

The surprise move on Monday appears to vindicate Apple’s argument, which is that the U.S. government had not exhausted all available means to recover information from the phone.

It stands in contrast to assertions made by FBI Director James B. Comey, who this month testified that bureau officials “have engaged all parts of the U.S. government” to ask “does anybody have a way, short of asking Apple to do it,” to unlock Farouk’s phone. “And we do not,” he said.

Similarly, FBI supervisory special agent Christopher Pluhar said in a court filing that the bureau had “been unable to identify any other methods feasible for gaining access.”

An Apple attorney noted that such statements were “the fundamental predicate” of their motion to seek Apple’s aid.

In a conference call with reporters, a second senior law enforcement official repeatedly said that “the FBI has been continuously working on all different avenues” on how to unlock the phone throughout the litigation.

He declined to offer details about who had come forward with a solution and whether it involved a vulnerability with Apple’s software.

If it’s the latter, a second Apple attorney said, they would like the government to provide details. “We have never said that our software is perfectly safe and secure,” the attorney said in a conference call with reporters.

A number of cryptography experts over the past month have described ways in which the FBI could try to unlock the phone without Apple’s help. They included exploiting bugs in Apple’s software, making copies of the phone to try cracking the passcode, and using electron beams or radio waves to try to obtain the encryption key from the phone’s chip.

The second law enforcement official declined to say whether it was a lost opportunity for the government to establish a legal precedent that authorities, under the All Writs Act, may force a company to provide technical help in unlocking an encrypted device.

“This is about getting into a terrorist’s phone,” he said. “It’s always been about this phone and the evidence that may be on it.”