The Justice Department filed a letter in a US District Court on Friday telling a judge that it still wants Apple to extract pictures, text messages and other digital data from an iPhone used by someone accused of trafficking in methamphetamines.

Also on Friday, court documents were unsealed showing that Apple rebuffed an order to help break into a locked iPhone for police investigating criminal gang activity in Boston.

The news came after a high-stakes showdown between Apple and the FBI over access to the iPhone of a California gunman ended with investigators saying they had extracted the data on their own.

Timing in the Massachusetts case lent support to Apple's ongoing argument that the US government was out to set legal precedent that would essentially open a back door into all iPhones.

A judge in Boston on February 1 ordered Apple to help police extract data from an iPhone confiscated last year from an alleged gang member, according to documents posted online Friday by the American Civil Liberties Union.

Apple told AFP it immediately challenged the order on legal grounds, and advised the court it could not unlock the handset because it was powered by iOS 9 software with updated security features.

The deadline passed for the US government to respond to Apple's stance on the order, indicating the effort was dropped.