If the terror attack in Australia succeeded, airplane passengers may have found themselves being gassed. More details about the foiled terror threat surfaced recently after Australia’s counter-terrorism operations across Sydney.

According to The Australian, multiple sources told them that the alleged terrorists were creating a “non-traditional” device that would emit a toxic, Sulphur-based gas that would kill all flight passengers. The four men who were arrested in Australia’s counter-terrorism operations were all working on creating the poisonous gas device, multiple unnamed sources told The Australian.

The West Australian reports that a flight heading to a Jakarta to Sydney route was possibly the terrorist’s target. Police found a flight number heading to the said destination during their counter-terrorism raids.

Aside from the non-traditional gas device, police say a crude homemade bomb would be used in the terror attack. The bomb would be disguised inside as a kitchen mincer.

According to News AU, incoming Home Affairs Minster Peter Dutton said terror threats will only increase from this point onwards. “This threat is not going to go away, it’s going to increase,” Dutton said.

Australian police conducted their “major joint counter-terrorism operation” across Sydney. The four suspects were nabbed in Surry Hills, Lakemba, Wiley Park, and Punchbowl. The terror threat is suspected to be linked to ISIS.

One of the nabbed suspects denied links to terrorism, reports ABC. “I love Australia,” said the man nabbed from Surry Hills.

Following reports of the foiled terror attack, added security measures for domestic flights was announced. Qantas and Virgin announced that passengers are now required to arrive for their flight two hours before departure for additional security measures. Though no changes were made on what items can be carried, passengers are advised to limit their baggage and carry-on items for a faster and more efficient security screening.