Residents have been warned to not eat seafood caught near the Brisbane River due to a potentially toxic chemical spill.

The warnings came as thousands flocked to supermarkets to snap up fish for their Good Friday feasts.

The Queensland Government has launched an investigation after fire-fighting foam leaked into waterways from Brisbane Airport, suspected to be the cause of a small fish kill.

View photos Brisbane residents were warned not to eat seafood caught near the mouth of the river after a potentially toxic chemical spill. Picture: 7 News More

The chemical PFOA is found in a fire-fighting foam used at airports and defence sites.

On Monday a Qantas sprinkler system failed, releasing 22,000 litres of it - about a quarter of which is estimated to have leaked from the hanger into the water way.

But it took the government five days to alert the public of the possible threat.

"We notified the Queensland Government and we're working with Brisbane Airport on the clean-up and the investigation," a Qantas spokesperson said.

View photos On Monday a Qantas sprinkler system failed releasing 22,000 litres of fire-fighting foam - a quarter estimated to have leaked from the hanger into the water way. Picture: 7 News More

The use of this particular type of foam is banned is Queensland. However because the airport is Federal land the airline wasn't breaking any laws by using it.

Recreational fishers are being urged to avoid the lower reaches of the Brisbane River from Bulimba Creek to Fisherman Island and north to Shornecliffe.



Seafood caught in the region since Monday should not be eaten.



Environment Minister Steven Miles said the affect the chemical has on humans was unknown.



View photos It took the government five days to alert the public of the possible threat. Picture: 7 News More



"It's likely these chemicals have been greatly diluted. The evidence between these chemicals and health risks are still inconclusive.

"There is some evidence from the United States that these chemicals can cause certain types of cancers [but] it's inconclusive," he said.

People are being urged to avoid the area until the investigation is over.