A senior ISIS commander sent parts to make an improvised explosive device (IED) to the two men who were arrested in connection to an alleged plot to take down a passenger plane, Australian police said Friday.
The accused were also involved in another scheme to release a toxic gas in public, Australian Federal Police Deputy Commissioner National Security Michael Phelan said at a press conference.
The plan to bomb the airliner was one of the "most sophisticated plots that has ever been attempted on Australian soil," Phelan said.
The components of the IED were sent through international air cargo by the ISIS operative to the accused men, Phelan said. The two were charged with terror-related offenses Thursday.
The accused men received the parts in Australia and assembled what police believe was a "full functioning" IED, he said.
They attempted to take the device on an Etihad Airways flight on July 15, but the plan was aborted. "At no stage did the IED breach airline security," Phelan said.
Australian Federal Police say the planned airline attack was one of two alleged plots the men have been charged in connection with.
The second terror plot uncovered in the past week by police involved an attempt to create a "improvised chemical dispersion device" to release hydrogen sulfide, Phelan said.
However, due to the difficulty of producing the highly toxic chemical, there is no evidence that the device was completed, he said.
"We were a long way away from having a functional device," Phelan said.
Two search warrants of properties in connection to the case are ongoing, he said. One man remains in police custody, and a fourth has been released.
Multiple raids have been carried out at multiple properties across Sydney by law enforcement authorities since Saturday, including the suburbs of Surry Hills, Lakemba, Wiley Park and Punchbowl.
Investigators were seen rifling through garbage and removing items from houses, dressed in full protective gear.
Threat level lowered
Earlier Thursday, Turnbull said the threat to aviation in Australia had been "disrupted and contained" following the arrests and the level of security at airports was being lowered.
Stricter airport security measures had been put in place following the attack, with Australian airports warning of possible delays and longer check-in times.
Developing story -- more to come