Victoria's chief health officer has warned of a potential measles outbreak after two cases were reported in Melbourne's south-east.

Professor Charles Guest said the two teenage siblings from Rowville had just returned to Australia from Kuala Lumpur.

They travelled on Air Asia flight D7214, which arrived at Tullamarine at 9.30am on January 5.

Professor Guest said before they were diagnosed the children visited Fountain Gate Shopping Centre and a cinema with their family.