KARACHI: Pakistan's top investigation agency arrested six people on Friday for their alleged involvement in a scandal involving fraudulently obtained pilots' licences that came to light after a Pakistan International Airlines jet crashed last year, officials said.

"Five Civil Aviation Authority (CAA) officials and a pilot have been arrested," the Federal Investigation Agency (FIA) said in a statement, adding at least 40 pilots and eight officials from the CAA's licence branch have been named in three cases registered by the agency's corporate crime wing.

An inquiry into the crash in Karachi in which 97 people were killed pointed to the pilots not following procedures, while a minister said the voice recorder suggested the pilots were distracted by a conversation about the COVID-19 outbreak.

Following the crash, Pakistan opened criminal investigations into 50 pilots and at least five civil aviation officials who allegedly helped them falsify credentials to secure licences.

"We have found a money trail in the investigation, each pilot paid a minimum of $312.50 for each paper they were supposed to appear in," Abdul Rauf Shaikh, a senior FIA official, told Reuters.

The scandal has tainted Pakistan's aviation industry and especially flag carrier Pakistan International Airlines (PIA), which has been barred from flying to Europe and the United States after dozens of its pilots were named in an initial list of 262 with "dubious" licences.