Police continue to search homes of four men arrested in connection with plot.

Security lines stretched out the doors at Australia’s major airports as travelers faced tighter screening after police thwarted an alleged plot by Islamist-inspired militants to bring down a commercial airliner . Prime Minister Malcolm Turnbull declined Monday to comment on local news reports that four men detained in Sydney over the weekend by counterterrorism police planned to kill everyone on board a passenger aircraft using toxic sulfur gas or an improvised bomb, hidden inside a kitchen meat grinder carried on board. The Wall Street Journal wasn’t able to independently verify the reports of the alleged plot.

“I can’t say precisely how far they were advanced at this stage, because that’s a matter that’s being investigated. Mr. Turnbull told Australian national ABC radio. But I can say that certainly the police will allege they had the intent and were developing the capability.” Mr. Turnbull hinted that the information that led to the sweep came from another government. “We have very fine intelligence services. But every nation depends on the work of others,” he said. “We are intensifying, all the time, our collaboration with other countries and other agencies, because with the threat there are no borders. Nowhere is far away from anywhere else nowadays.” Australia is a member of the Five Eyes intelligence-sharing alliance together with the U.S., Canada, New Zealand and the U.K. It has less formal intelligence-sharing agreements with other countries including Germany, France and the Netherlands.

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