Reports of hundreds of dead fish littering the banks of the Brisbane River since Friday have prompted an investigation by state wildlife authorities.

An Environment Department spokeswoman said it had responded to reports of dead fish around St Lucia, Yeronga, and Indooroopilly.

“Our officers have been deployed to inspect the areas where dead fish have been reported, and will collect water and fish samples for further analysis,” she said.

Residents reported additional sightings further upstream, extending past Chelmer as far as Seventeen Mile Rocks.

Theories about run-off or construction debris leading to toxic water conditions were raised online by concerned residents, while authorities said fish deaths could be caused by “a range of environmental factors”.

“A potential cause of [these] deaths may be the recent heavy rain, which has washed organic matter into the river, resulting in low dissolved oxygen levels,” the department spokeswoman said.

She added that the investigation was continuing, and urged anyone with relevant information, including further sightings of dead fish, to contact the department’s pollution hotline on 1300 130 372.

Brisbane City Council declined to comment on the matter.