It's still not clear how 16 horses died while returning to Melbourne from a polo tournament in Tasmania.
The horses were reported dead last Monday after being shipped to Melbourne on the Spirit of Tasmania.
The animals had also been on the road in Victoria but it wasn't clear when they died, an Australian Maritime Safety Authority spokeswoman told AAP.
The ABC reported the animals were from the Willo Polo club in NSW and competed at the Barnbougle Polo event in Tasmania on January 20.
A representative from Willo Polo told the broadcaster the investigation was "in the hands of authorities" and the club was "hoping to find out what happened".
The Department of Primary Industries, Parks, Water and Environment is investigating, with the assistance of the Australian Maritime Safety Authority.
