Prime Minister Malcolm Turnbull said the incident was "not now being treated as terrorism-related".
Malaysia Airlines flight MH128 abandoned its planned trip to Kuala Lumpur on Wednesday night and turned back to Tullamarine Airport after the man was restrained by other passengers.
Flight 128 to Kuala Lumpur, Malaysia, was forced to return to an Australian airport after a 25-year-old Sri Lankan man began shouting on board.
When the man charged the aisle and tried to enter the plane's cockpit, passengers and crew aboard the flight stirred to action and were able to wrestle him to the ground.
Videos posted to social media show the suspect tied up and face down, with a crew member bracing himself against his back and a passenger sitting in the seat above him. "He was essentially trussed up as the flight returned to Melbourne". "The device was described as an amplifier type instrument.it can potentially be wired up and dealt with in a unsafe manner". Passenger Andrew Leoncelli described it as a Boombox portable music player. "He goes "No, I'm not going to sit back down, I'm going to blow the plane up", he told 3AW. "He was agitated, is the best description -100 percent, he was agitated".
"Two or three courageous young Aussies have taken him on and got him to the ground".
Malaysia's deputy transport minister said the device was some kind of mobile phone charger, while Victoria Police superintendent Tony Langdon said the item was something one would "carry around on a regular basis".
"Counter-terrorism response and protocols kicked in. for us that meant having the plane isolated, and as soon as practicable, getting the passengers off the plane safely and dealing with the offender", Ashton said.
The airline said the man was apprehended by airport security after the plane landed and was sent to a remote part of the airport.
While officials played down the incident, passengers spoke of a terrifying 90-minute ordeal after the plane took off.
Police said Marks was carrying a Bluetooth speaker or something similar.
Victorian Premier Daniel Andrews said Thursday that passengers and crew were being offered support after the "frightening" experience.
"We don't want to be stigmatizing any more than mental illness is already stigmatized", he said.
"If we had an incident where there were further explosives that were triggered, we could have had a mass casualty incident", Ashton said, defending the move.
Malaysia Airlines has suffered two major disasters in recent years.
It added: "Malaysia Airlines would like to stress that at no point was the aircraft hijacked".