1 of 4 men arrested in Australia terror raid released Three of the men remain in custody, and one has been released, police said.

 -- One of four men arrested Saturday in Australia in connection with a plot to bomb an airplane was released from custody without being charged with a criminal offence, the New South Wales Police Force announced Tuesday.

The three other men remain in detention.

The men were arrested following an investigation into allegations that they had intended to commit terrorism using an improvised device, one that the U.S. State Department said was likely built to be stored inside a meat grinder.

U.S. officials had previously told ABC News that items found in the possession of the men indicated some form of plotting involving smuggling something on board an airplane.

The State Department’s Overseas Security Advisory Council, which offers info and analysis to government and private-sector partners regarding security issues abroad, previously issued a notice outlining the “potential aviation threat disrupted in Sydney.”

“Australian authorities have detained at least four men in greater Sydney for attempting to build an improvised explosive device that they could smuggle onto an airplane. The disrupted plot -– the details of which are still developing -– serves as a reminder that while recent attacks in Australia have tended toward low-skilled attacks using basic weapons, ISIS-inspired extremists have not abandoned more sophisticated plots, such as those involving aviation,” the State Department notice said.

It's unclear whether or not the men who were detained have any connection to any transnational terrorist organizations like ISIS, according to the notice.

“As with the intended target, early reporting reflects competing claims on the nature of the improvised explosive device and its method of deployment," the notice said. "The general consensus is that the device was designed be smuggled aboard a plane inside a meat grinder.”

ABC News' Joshua Hoyos contributed to this report.