Word first emerged about the discovery of dead fish in the small community of Marlinja, south of Katherine, on January 15.
The community, located on Newcastle Waters cattle station, had received massive downpours of rain as a tropical low began to move inland over the Northern Territory.
Katherine-based animal vet and Protect Big Rivers environmental group member, Samantha Phelan, said she received a call from concerned residents.
"They'd gone down to the creek that morning and seen a whole heap of dead fish up and down the stream," she said.
Dr Phelan said she was referred to a hotline to report the incident.
Her call was then answered in Melbourne, about 3,000 kilometres away.
"I was then contacted by fisheries the following day," she said.
"So now we're at 48 hours from when the fish began to die."
But it wasn't until four days after her report that officials assessed the site, which Dr Phelan said was concerning.
"I think that's really incompatible with a good regulatory regime."
Timely data needed
Dr Phelan said she was concerned about the quality of the data collection.
She said reaching an accurate conclusion about the cause of death was difficult unless the site was investigated swiftly in a waterway where conditions could quickly change.
Her view was supported by University of Sydney School of Engineering head Stuart Khan, whose research has focused on water quality and environmental water systems.
"You need to collect the water data and any other ambient data quickly or you won't have the full information to be able to understand exactly what occurred," Professor Khan said.
He said he hadn't seen footage or attended the site and had not speculated on the cause of the fish kill.
He said monitoring of any fish kill relied on quality data taken in the first 24 to 48 hours of the event.
"That's because things like dissolved oxygen concentrations, bacterial activity and water can all change quite quickly within that type of time frame," he said.
Professor Khan said quick responses from the government ensured public confidence in the ability to monitor water quality.
"[It] relies on several things, including an observation that governments are following up and investigating when impacts occur, but also rapid communication, timely communication so that communities are not kept in the dark," he said.
What the government found
The Department of Environment, Parks and Water Security was tasked with collecting samples.
The water samples came back "clean", it told the ABC in a statement, with "no indication of pollution or water quality concerns".
The cause of the fish kill was not clear.
The department said it had provided its sample results to the aquatic biosecurity team.
"Aquatic Biosecurity are continuing their investigation to try and determine a cause of the dead fish, but as of yet no cause has been identified," the statement read.
The environment officials said fish kills were common in the "first flush" of the Top End wet season due to low-oxygen conditions created by decomposing organic matter.
"Although the cause of fish death is not established yet, fish kills are frequently reported in the Top End of the Northern Territory during the early wet season," the statement read.
They said officials had attended the site despite poor weather at the time.
Concerns had been raised by some people the ABC spoke to regarding fracking sites operated by Tamboran Resources 60 kilometres from Marlinja and whether its activity could have impacted the water.
Tamboran told the ABC linking the fish kill to its work was baseless.
"Fish kills are relatively normal during changing weather conditions like flooding and heatwaves," a company spokesperson said.
"Any linkage to Tamboran's operations is baseless and can only be intended to create fear within the community."
Traditional owner alarmed
Jingili elder Uncle Samuel Janama Sandy said he was connected to Marlinja through his family and grew up in the small community.
He said he wanted to see closer monitoring of fish kills.
"The Northern Territory should be monitoring these events," he said.
"During floodwaters time, they should be there on the ground and monitoring."
A man sits outside his home looking off into the distance
Samuel Janama Sandy wants better monitoring of fish kills.(ABC News: James Elton)
The director of the Nurrdalinji Aboriginal Corporation said the cultural impact of fish kills in the area were felt deeply by Aboriginal people.
"Water is very important, we took care of it," he said.
"Make it safe and clean."