According to a report in The Age, metal filings were found by Saputo staff members in a tanker at its Leongatha factory in March.
Curdled milk was reported in a separate incident at its Cobram facility in January.
The tankers were allegedly supplied by Maffra-based Bulk Liquid Carriers Pty Ltd (BLC).
Dairy Food Safe Victoria has confirmed it is investigating whether Saputo Dairy Australia products had been transported by an unlicensed trucking contractor in unclean tankers.
The tankers are alleged to have also carried food waste and animal stockfeed.
Saputo declined to comment on whether or not it had suspended BLC services to its plant.
“Saputo Dairy Australia takes all food safety and quality allegations extremely seriously,” it said in a statement.
“We are investigating allegations made against a third-party contractor and our objective is to bring clarity to the situation as soon as possible.
“We are also working with the industry regulator, Dairy Food Safety Victoria, as they conduct a parallel investigation.
“In the event there is any legitimacy to the allegations, we will take the necessary steps to address such matters as needed.”
Lachlan Wigg and business partner Patrick Gray own a company that holds 50 per cent of the shares in BLC.
Mr Gray would only say “No comment” when approached by Stock & Land to discuss the allegations.
Mr Wigg and Mr Gray also supply Saputo milk from their substantial dairy farming enterprise in the Macalister Irrigation District (MID).
They bought five neighbouring dairy farms in the area totalling 700 hectares for about $13 million in 2014.
Those farms were fined just under $16,000 for two illegal effluent-dumping incidents in the space of three months in 2017/18.
VicRoads brought successful prosecutions against another Wigg-Gray company, Ag-Spread, in which it was fined $95,000 for 85 breaches of driver safety laws.