NEW YORK (REUTERS/BLOOMBERG) - The United States Justice Department on Friday (April 22) dropped its effort to force Apple Inc to help unlock an iPhone in a drug case in New York after someone provided authorities the passcode to access the device.

In a letter filed in federal court in Brooklyn, New York, prosecutors said that investigators late on Thursday used that passcode to access the iPhone that was used by a drug dealer.

"Late last night, the government used that passcode by hand and gained access to the iPhone," the US said in the court filing on Friday.

"Accordingly, the government no longer needs Apple's assistance to unlock the iPhone, and withdraws its application."

The case gained further significance after prosecutors in March dropped a similar effort to force Apple to help access an iPhone used by one of the shooters in December's San Bernardino killings, after a third party provided a way to crack it.

The drug dealer's iPhone is just one of more than 1,000 Apple phones that cops around the US say they cannot break into, but it has been at the epicentre of a legal fight over privacy and security that may redefine the relationship between the police and the public.

Justice Department spokesman Emily Pierce said the cases have "never been about setting a court precedent; they are about law enforcement's ability and need to access evidence on devices pursuant to lawful court orders and search warrants".

An Apple spokesman declined comment.

Prosecutors had been challenging a Feb 29 ruling by US Magistrate Judge James Orenstein holding he did not have the authority to order Apple to disable the security of an iPhone seized in a drug probe.

The case predated the government effort to force Apple to help access the phone of Rizwan Farook, one of the two killers in the San Bernardino massacre, which left 14 people dead and 22 wounded.

While the Justice Department dropped that bid after a third party provided a way to access the San Bernardino phone, it continued appealing Judge Orenstein's ruling.

FBI director James Comey has said that the method used on the San Bernardino iPhone 5c would not work on other models, including the iPhone 5s, the type in the Brooklyn case.

That phone belonged to Jun Feng, who has pleaded guilty to participation in a methamphetamine distribution conspiracy, which prosecutors are continuing to investigate.

Unlike the phone used in San Bernardino, Feng's phone had an older operating system, iOS 7, which is not protected under the same encryption technology, which is why Apple could access it.

Apple has some 70 times before the Brooklyn case emerged helped the authorities access data on iPhones, according to court filings.