Australia terror probe: Man released without charge

Australian police continue to gather evidence about the alleged plot

One of four men arrested over a suspected terror plot to bring down a plane has been released without charge in Australia.

Police have been gathering evidence since conducting raids at the weekend in what PM Malcolm Turnbull called a "major counter-terrorism operation".

Investigators allege the plot involved an improvised explosive device.

A 50-year-old man was released by police on Tuesday, but three men remain in custody. No charges have been laid.

The men can be held for seven days without charge after a magistrate on Sunday granted police special powers.

"This investigation remains ongoing, and further information will be provided at an appropriate time," the Australian Federal Police (AFP) said in a statement on Wednesday.

On Sunday, AFP Commissioner Andrew Colvin said authorities had intervened early without having "all the pieces of the puzzle" because it was a counter-terrorism investigation.

Details remain unclear

Local media reported the men planned to use poisonous gas or a crude bomb disguised as a meat mincer, but police have not confirmed details of the allegations.

Mr Turnbull said the suspected plot was "advanced" and driven by "an Islamist extremist motivation".

On Tuesday, Etihad Airways confirmed it was assisting police with their investigation.

Enhanced security measures at Australian airports have caused large queues

"Etihad is complying fully with the enhanced security measures at airports in Australia and monitoring the situation closely," the airline said, without giving further details.

Australia's national terror threat level remains at "probable" - the third level on a scale of five.

The nation's airports have increased security measures, leaving passengers waiting in lengthy queues after being advised to arrive earlier than usual.