Patrick Pak Lamb Li, 54, of Padstow, and Singaporean national Keng Chuan Koh, 30, were arrested in North Geelong in December 2006 after passing police stopped to help them with their broken-down van.

Officers allegedly found 340litres of liquid ecstasy chemical MD2P, worth an estimated $51million when converted into tablets.

Both men were charged and sentenced to jail in Victoria.

Further investigation by detectives of the Asian Crime Squad led police to a storage unit at an industrial complex on Victoria Avenue, Castle Hill, where they said they found 1900 litres of the same chemical in boxes in January 2007.

It is alleged the quantity could make about two tonnes of ecstasy tablets with an estimated street value of $540million the biggest drug seizure in Australian history.

The men were brought from Victoria to Sydney last Wednesday and charged with supplying and possessing a large commercial quantity of a prohibited drug, participating in a criminal group/contributing to criminal activity, making a false statement and using a false instrument.

They were refused bail and are due to appear at Parramatta Local Court on March25.

Strike Force Trentham, comprising detectives from the State Crime Command Asian Crime Squad, was set up in January 2007 to investigate the alleged possession and supply of prohibited drugs.