“The animals were being killed for no other reason than that they were found to be underperforming.”

It is "highly probable" that between 2009 and 2013 at least 99 greyhounds were killed - most by a "blow to the head" - and buried at a Hunter Valley, NSW, training track, an independent investigation has found.

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Almost all of the dogs excavated from Keinbah Trial Track had “no evidence of any other injury occurring around the time of death” but were killed either by a gunshot or blunt instrument and suffered "major skull trauma", the report's author, Clive Steirn SC, said in a statement.

“Logically, the only probable motive for culling greyhounds in these circumstances leads to a conclusion the animals were being killed for no other reason than that they were found to be underperforming after being trialled, and therefore of no further use,” he said.

The report has recommended Greyhound Racing NSW demand a number of individuals "show cause" as to why action should not be taken against them for breaching industry rules.

It didn't take investigators long to find the skulls and bones buried just centimetres below the surface, the property's current owner Natina Howard, who was not involved in the mass burial, told the Maitland Mercury.

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"Within 10 to 15 minutes of walking on to the property, they found the first mass grave site," said Howard, who bought the property and track with her husband in December 2013.

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