Importing to Australia is stricter than other popular destinations and are subject to biosecurity control. Australia does not allow entry of items with soil, dust and organic insects, such as beds for pets, flower pots and bicycles, etc., All goods must be clean and dry.
If items of biosecurity concern are found and cannot be released immediately, your options may include (at your expense):
treating the goods, providing a suitable treatment is available
exporting the goods from Australia, or
destroying the goods.