Authorities say the material, which has sparked a series of raids targeting businesses and individuals, could have resulted in enormous harm to Australia's biosecurity.
In all, 38 tonnes of hazardous material has been seized, enough to fill seven 20-foot shipping containers.
The material also included pig meat, beef and plant roots covered in soil.
The haul was discovered after a biosecurity officer noticed suspicious boxes of goods during a routine inspection in NSW, the federal agriculture department said on Monday.
The department then executed a warrant at a western Sydney warehouse on February 17.
About 250 tonnes of goods were carefully examined with more than 38 tonnes deemed a biosecurity risk.
A few days later, Australian Federal Police helped execute other warrants at various locations across the state.
"A number of warrants have been executed in relation to individuals and businesses in relation to the investigation," the department said.
Australia's Director of Biosecurity Andrew Metcalfe said anyone convicted of deliberately flouting biosecurity laws can be jailed for up to 10 years.
Individuals can be fined more than $1 million and companies almost $6.9 million.
"The secured goods could have posed an unacceptable risk of introducing disease and pests for plants and animals alike," Mr Metcalfe said.
The investigation is ongoing, with the seized imports being managed by the department.
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