UPDATE 2:10PM: Victoria Police has confirmed that "there is no genuine threat to Melbourne and Avalon Airport. There is no credible information to suggest there was any strength behind the threat made at this stage."
UPDATE 1:48PM: Victoria Police Assistant Commissioner Andrew Crisp will make an announcement about the Melbourne Airport bomb threat at 2:15PM.
UPDATE 1:15PM: Victoria Police has issued a brief update on the ongoing bomb threat investigation at Melbourne Airport.
Victoria Police is currently responding to an anonymous threat made against Melbourne and Avalon airports. Police are assessing the threat and working closely with the AFP and airport security to ensure community safety.
Victoria Police is still assessing the threat, however based on advice from Tullamarine and Avalon airports, there has been no change to flight schedules.
UPDATE 12:40pm: Qantas has confirmed "Business as usual for Qantas services from Melbourne Airport and for Jetstar services at Avalon".
UPDATE 12:35pm: Avalon Airport CEO Josh Giddings has told the Geelong Advertiser: "It's an unspecific threat. They don't actually say what they're going to do. Consequently we've increased security and we've asked the Australian Federal Police to increase their security.''
Melbourne Airport's website shows flights are still landing and departing while police carry out their investigations.
UPDATE 12:29pm: Virgin Australia says its flights are running on schedule at present despite the ongoing bomb threat investigation at Melbourne Airport.
Avalon Airport is reportedly treating the threat as non-genuine, however it says passengers will see greatly increased numbers of security personnel for at least the next week.
UPDATE 12:12pm: Melbourne talk-radio station 3AW says it has received information that the threat is "non genuine", however Victoria Police says it is still investigating, and issued the following statement to Australian Business Traveller:
"Victoria Police is currently responding to an anonymous threat to two Melbourne airports - Tullamarine and Avalon. Police are assessing the threat and working closely with AFP and Airport Security to ensure community safety."
The threat was apparently delivered as a letter to The Herald Sun and other media outlets, prompting state and federal police to swarm the airport.
The Herald Sun said the letter provided specific details about what weapons were to be used.
Australian Business Traveller expects flight delays at the airport -- we have contacted Qantas and Virgin Australia for comment on how the airport closure will affect their passengers. Both airlines were unable to immediately respond.
Melbourne Airport has reportedly received a bomb threat and passenger movements are currently frozen as police investigate.
Corporate affairs staff at Tullamarine were not able to immediately confirm details of the threat but said they would provide further details shortly.
Geelong's Avalon Airport is also reportedly targeted by the same threat.
-- more to come --