A health warning put in place because of high contamination levels in Ngongotaha Stream will not be lifted until the source of contamination can be identified, a health official says.
But some locals are saying they will not stop using the waterway until people start getting sick or "fish start turning belly up".
Toi Te Ora Public Health Service issued the health warning on Tuesday, stating there were elevated levels of bacterial contamination in the stream, increasing the risk of water users getting sick or contracting infections.
The warning was issued for the section of the stream near the railway bridge.
An A4-size laminated sign has been posted on the end of the bridge.
Toi Te Ora medical officer of health Dr Phil Shoemack said the decision to warn the public came after regular water samples showed high levels of contamination.
"The stream is regularly sampled by the Bay of Plenty Regional Council so we monitor that and recently we have had a few come back in the red zone, meaning they were full of bacteria."
He said further investigations would be carried out to determine what was causing the contamination. "Until we do find out the cause, the safest thing to do is to keep people out of the water. The warning will not be uplifted until we are able to determine the source."
Talita Adams has lived in Ngongotaha all her life and said swimming in the stream was a regular summer activity.
"A group of about 10 of us went swimming in the stream on Monday.
"This was before the warning was put out so we didn't know better but in saying that, none of us are sick."
Ms Adams said the group was in the water for at least two hours on Monday and they had been regularly swimming in the same spot for the past month.
"From what I've heard, people are not taking the warning very seriously because nobody has got sick yet. Until somebody does we'll probably keep going back there."
Another resident said she had been fishing in the stream for more than 20 years and had never been sick from eating the trout.
"If the water was contaminated then there would be fish turning up dead, but they're not.
"Not where I fish anyway. I'm fishing considerably more upstream than where they did their water analysis so I'm not worried. I won't stop fishing until the trout start turning belly up."