An Auckland-bound Air New Zealand flight was evacuated at Melbourne airport after a white substance was found on board.
Around 20 passengers were evacuated from flight NZ124 and quarantined on Monday afternoon (local time).
An Air New Zealand spokeswoman said the flight was delayed as a result of a potential security issue.
"The flight was later cancelled as, unfortunately, the delay meant the crew had exceeded their crew hours limitation," she said.
She said the customers were being accommodated on other services and Air New Zealand apologised for any inconvenience.