It is enough to make any bread-lover's stomach churn.

While unpacking the groceries with a friend on Sunday, a Townsville woman noticed a suspicious-looking hole in a loaf of Helga's bread she had bought.

"I said to my friend, this bread's got a hole in it, it looks like a rat's eaten into it," the woman, who asked not to be identified, said.

The rat had done more than chew through the packaging; when she lifted the bag out she found the rat alive and nestled inside the loaf.

"The thought of a live rat in my loaf of bread and so close to me was pretty gruesome," she said.

"I didn't want to vomit, I just wanted to throw it away, I got all squeamish."

The woman said she took the bread, and rat, back to the local Coles supermarket where she had bought it but was not satisfied with the management's response.

"They said 'that's not our house bread so we wouldn't be responsible for that'," she said.

"They didn't apologise, they didn't say they were sorry about it, all the manager said was that he didn't know how to handle the situation."

She said she was not seeking compensation and had declined the manager's offer of a store credit.

A Coles spokesman said the incident was "obviously concerning" and an internal investigation was underway, but it appeared the contamination occurred during transit.

"It is certainly unfortunate but we are confident it is an isolated incident."

The woman also reported the incident to the Townsville City Council, which investigated the complaint but found the supermarket met all the relevant health requirements.

A spokesman for Goodman Fielder, which owns Helga's, said he was confident the rat did not enter the package at the company's bakery.

"It obviously didn't happen during the baking, slicing or packing process," he said.

"If it has happened, it must have happened at some point in the supply chain and we have no control over that."

AAP