Any decision on action against Mr Hilliam would be made after HNZPT had followed up their letter with Mr Hilliam, with whom HNZPT had corresponded several times before over different matters.
Mr Hilliam has claimed that pre-Maori inhabitants of Northland were of Celtic and Mediterranean origins, and has released two drawings that he says are visual reconstructions produced from two skulls by a forensic expert.
The skulls were supplied by Mr Hilliam, who says he has had them since the late 1990s.
The veracity of the "expert" drawings has been questioned, with Mr Hilliam saying the expert has links to a university in Edinburgh.
However, the city's main university - Edinburgh University - has told the Northern Advocate they are unaware of the drawings.
A Northland history expert said New Zealand's past was fascinating as it is, without "making up alternative histories of Celts, Egyptians, Phoenicians and Greeks arriving here".
Bill Edwards, the Northland manager for Heritage New Zealand Pouhere Taonga (HNZPT), said there was no evidence of pre-Maori inhabitants in New Zealand.
"Maori were the first humans to colonise New Zealand. The multiple strands of evidence consistently show that they arrived just before the Kaharoa eruption.
"There is no evidence of people arriving before the Maori in the archaeological, linguistic, geological, biological or environmental records.
"The story of New Zealand is fascinating without making up alternative histories of Celts, Egyptians, Phoenicians and Greeks arriving here."
Mr Hilliam's claims prompted a strong reaction from some sectors of the archaeological community, with some saying racial and political motivations were behind his release of the drawings.
"I'm not a racist. I have two Maori son-in-laws, I'm friends with a lot of Maori people. I am not a racist," Mr Hilliam said.
"I'm really interested in the true early history of New Zealand, particularly in the ships that came to New Zealand that got wrecked and never left," he said.
In a May 25 letter to the Northern Advocate, Mr Hilliam said there should be a Royal Commission of Inquiry into the true early history of New Zealand.
"The party that includes this in their election manifesto will be clear winners."
Northern Advocate editor Craig Cooper last week apologised for the paper's May 13 publication of a story on the matter before it had received word from Edinburgh University about Mr Hilliam's claims.
"Some counter claims to Mr Hilliam's theory to provide some balance should have been included."
Mr Cooper said it was healthy for Northland to examine its past, but the paper was now acutely aware that the sensitive nature of history meant balanced reporting was important when doing so.