Thirty-six gravestones were destroyed during the incident at Singleton on the evening of May 31, with many pushed over and smashed.

Police are treating the matter as a case of malicious damage.

Investigators were told a vehicle was seen parked at Sedgefield cemetery between 7pm and 7.15pm.

Police are appealing for anyone who witnessed the incident, or who may have noticed any suspicious activity in the area at the time, to contact them.

Hunter Valley Police District Commander Superintendent Chad Gillies said he hoped people would come forward with the information police needed to find those responsible.

"We want to find answers for the families affected by this," he said.

"They have already experienced immeasurable grief.

"And, this sort of incident stirs up those emotions all over again.

"Someone knows something, and we urge anyone with any information to speak up."

Anyone with information is urged to contact Singleton Police Station on 6578 7499 or Crime Stoppers on 1800 333 000.