A fatty, smelly substance found on a beach south of Napier last month likely came from a Hastings District Council wastewater outfall, the council has confirmed.

Previous test results showed the substance found on Haumoana beach on December 1 was a waste byproduct from animal or food processing, and also contained hydrocarbon.

At least two dogs became sick after eating it.

Hastings District Council contractors had been working on the outfall the previous day when they noticed “solid material discharging on the surface”, the regional council said in a statement.

“Contractors were undertaking annual maintenance of the outfall which involves flushing of this structure.

“This is a consented activity as part of maintaining the wastewater treatment plant and outfall.”

The test results confirmed it was consistent with a discharge of animal byproducts, and aligned with a discharge from the Hastings District Council wastewater treatment plant, it said.

Hastings District Council agreed that was probably the case.

“It is difficult to prove and there are other scenarios, however this does seem the most credible,” said three waters manager Steve Cave.

“While our processes for this work are set out in our resource consent and were strictly followed, council is keen to see how we can improve.”

It was not abnormal for animal byproducts to be found in the wastewater system, he said.

“Hastings District Council has a trade waste component, which is essential in a district that has such reliance on the processing of primary product, so it is not surprising to find it in the waste stream.”

The councils said they were working together to avoid it happening again.

By Lauren Crimp of rnz.co.nz