SYDNEY, Jan. 10 (Xinhua) -- A furore has erupted in the far west of New South Wales (NSW) State in Australia, after around one million fish were found dead in a 40-km passage of the Darling River in the township of Menindee, 1,150 km northwest of Sydney.

Rejecting the explanation given by authorities on Tuesday that the fish kill was a result of the ongoing drought, many local community members are now claiming the event was caused by water mismanagement.

With a build-up of toxic blue green algae, rapid temperatures changes can cause the plant to die.

When this happens and the organic material decomposes, a vast amount of oxygen is drawn from the water causing fish in the vicinity to suffocate.

While the State's Department of Primary Industry blames the lack of rain for the event, others believe that too much water was allowed to be taken out of the river for irrigators in recent years.

"What stinks more than this dead animal is the management of this river... and the absolute decimation of the river by cotton irrigators upstream," independent NSW Member of Parliament Jeremy Buckingham said in viral video posted to social media on Thursday.

"We have spent billions trying to save the Murray Darling Basin and what have we got? An ecological catastrophe! It's absolutely appalling!"

But NSW Irrigators' Council chief executive Luke Simpkins has refuted these claims and offered a different explanation for the distressing event.

"What has happened is as a result of the drought and no water flowing into the rivers," he told local media.

"This drought is a devastating time for all of us. This is not about diversions, but about inflows."

"Without inflows, blue-green algae events will continue to kill fish...and it should be remembered that irrigation farmers on the Upper Darling have not been allocated any water from the system for 18 months because of the drought."

In order to get to the bottom of the matter, state opposition leader Michael Daley, from the Labor Party, has called for a full investigation into the matter, with wide-ranging powers of investigation.

"The people of NSW have watched for 18 months as water theft scandals, water mismanagement and now ecological disasters have rocked far west rivers," he said.

"The scale of this disaster is extraordinary and unprecedented."

Among the fish varieties most impacted by the event are vitally important native species like bony bream, Murray cod and perch.