China has now suspended beef imports from a fifth Australian processor, John Dee Warwick, a single-family owned operation in Queensland's south east with 75 years in the game that sends product to customers around the world.
Chinese port of entry testing claims to have found a veterinarian drug called chloramphenicol and the Chinese are asking for Australian authorities to investigate.
Agriculture Minister David Littleproud said the plant now believes it has traced the source.
"We understand that this substance can occur naturally in some stockfeed and my department is working with the establishment to give Chinese authorities assurance around this incident and to have the establishment relisted after appropriate investigation," Mr Littleproud said.
Over the past 10 years, Australia's national residue survey has tested more than 3500 statistically viable random samples for this compound and had zero positive returns.
Australia's processing industry leaders say that survey is world-leading and underpins Australia's access to global markets.
Australian Meat Industry Council chief executive officer Patrick Hutchinson said his organisation was now 'working feverishly' with the company involved, Australian authorities and the importing jurisdiction to resolve the issue.
He made the point it would not be news if China was not involved, saying issues around adverse outcomes on port of entry testing occurred in the red meat trade on a regular basis.
"Various ranges of interventions are taken all the time. This is something we handle regularly and we believe this situation is one of those typical occasions," Mr Hutchinson said.
"We don't confirm or deny (the accusations being made by Chinese customs) but investigate and work through the issue as per process."
John Dee Warwick was contacted but has not made any comment yet.
Meanwhile, the four Australian plants slapped with suspensions from supplying China in May have put in place corrective programs which have been audited by Australian authorities and the corresponding report supplied to China.
They are now waiting on the results of the Chinese review of that report, hopeful of a lifting of the suspension. No time frame has been suggested.
Three of these plants are in Queensland and one in NSW and the issue was over labelling.