The Far North District Council has rejected social media claims on Monday that an undefined mess on the beach at Aurere, west of Taipa, was raw sewage from the Taipa wastewater treatment plant (which discharges into the Taipa River).
The council's general manager, infrastructure and asset management, Andy Finch, said on Tuesday that contractors had been sent to clean the beach, but whatever it was it would not be sewage from Taipa.
"There would have to be a massive failure of the system for toilet paper to get into the open sea then find its way to the beach at Aurere," he said, "and there has been no such failure."
It would not be possible for toilet paper to pass through the system and reach the river intact.
Allegations that sewage had polluted Aurere River were made in a video posted to a local Facebook community site on Monday night, the video-maker saying he had been fishing when he came across raw sewage, including toilet paper, along the banks of the river.
Mr Finch believed there were two possibilities — that someone had emptied the contents of a septic tank on to the beach, which he doubted, or that it was a type of seaweed that had washed up on coastlines in New Zealand in the past. It grew prolifically in nutrient-rich waters, and often turned white when it died.
"When broken up by waves and washed ashore this weed can look very much like paper, and I understand anyone seeing it might think the worst," he said.
"We are working closely with the Northland Regional Council to confirm exactly what the substance is and to track down its source."
Testing would take some time, but the results would be publicly notified when they were received.
"Whatever it is, it's nothing to do with the council," Mr Finch added. "We've sent contractors to clean it up though. It's not the sort of thing we like to see on beaches, and it's a particularly poor look with a long weekend coming up."
Meanwhile the video had been removed from Facebook on Tuesday, but not before it had been shared widely and viewed by many people.
"Ngati Kahu, and all residents, are naturally horrified at the thought raw sewage could be polluting the coastline and valuable food sources. I share that concern, and have instructed our contractors to remove the substance — whatever it is — as a precautionary measure," he said.