An unknown amount of milk from a new factory has spilled into the city's stormwater system.
The factory is today under investigation and could face a fine of up to $600,000 after council officers were tipped off and arrived at the Maleme St site yesterday.
Tauranga City Council staff were alerted to the spill at the newly established New Zealand Dairy Processing factory only after receiving information at 8.30am from a passerby who noticed dairy product in an open storm drain.
Tauranga City Council pollution prevention officer, Toby Barach, said it was not known how much of the long-life milk had escaped into the drain, which flows into the Waimapu Estuary, or what effect the contamination could have on fish life.
Mr Barach said large amounts of milk could suck oxygen from the water, killing fish life.
"At this stage there are no dead fish or dead eels, but that's not to say there won't be in 24 to 48 hours," he told the Bay of Plenty Times.
Mr Barach said when he and a Bay of Plenty Regional Council officer arrived at the milk plant, the company had already arranged a liquid waste-removal company to vacuum the milk from the drain.
Mr Barach said the company had not told the council about the spill, but New Zealand Dairy Processing general manager Stuart Gouk said yesterday that it had planned to.
Staff from both councils were still trying to determine the cause of the discharge, which was believed to have resulted from leaking cartons of ultra high temperature (UHT) milk and washdown from the plant floor.
Mr Barach believed there may have been a "glitch", where the plant's drain was connected to the stormwater drain.
Despite the foul odour it created, the spill was not believed to have posed any major health risk to people, Mr Barach said.
"Being a storm drain, it's unlikely you would have people swimming there."
Warning signs were already in place around the drain from a wastewater overflow, and the city council was yesterday considering erecting more near the estuary.
Water samples had been taken from the drain and would be tested over the next few days.
Discharging contaminants to city stormwater drains is illegal under the Tauranga City Council's Stormwater Pollution Prevention Bylaw and under the Resource Management Act enforced by the city council and regional council. Penalties under the Act ranged from a $1000 infringement notice to a maximum penalty of $600,000.
Mr Barach could not say whether New Zealand Dairy Processing would be prosecuted.
"Enforcement varies from an official warning to prosecution. It depends on the outcome of the investigation process and that's what we're going through at the moment."
Mr Gouk said the company was working with authorities but was not able to comment further.
"Until we get a response from the council, we can't comment. At the end of the day, we're trying to meet all requirements of the council."
Bay of Plenty Regional Council water-management group manager, Eddie Grogan, said it was investigating but would not comment until the process was completed.
New Zealand Dairy Processing has spent recent months converting the former Maleme St pet food plant into a modern milk-processing facility.
The company was incorporated on July 30 last year and then-Auckland businesswoman May Wang, who fronted Hong Kong-listed Natural Dairy's bid to buy the 16 Crafar farms, was named the only director.