The Zimbabwe Parks and Wildlife Management Authority (ZimParks) has announced that it has dispatched a team to conduct "broader" investigations at Lake Chivero after fish and wildlife succumbed to contaminated water over the past week.
Four white rhinos, three zebras, birds and livestock died after drinking cyanobacteria-contaminated water from the lake.
NewZimbabwe.com witnessed thousands of fish dead and dying over the weekend.
ZimParks spokesperson Tinashe Farawo in a statement said their first investigations have established that 1,000 fish died adding that sewage runoff from Marimba could be a trigger.
Farawo said even more fish might die.
"Preliminary investigations indicate that sewage runoff from the Marimba area has forced contaminated water into multiple bays, creating hazardous conditions for aquatic life.
"High pollution results in a boom in algae growth, this increases oxygen demand on the water body resulting in high mortality for the fish.
"As wind patterns continue to shift, we anticipate that this issue may further impact fish populations across the lake.
"In response, our team is currently on the ground carrying out further investigations on a broader scale," he said.
The authority recently blamed Harare City Council for discharging raw sewage into the lake which is a primary source of water and a popular recreational spot for Harare residents and other surrounding communities.
However, in an interview with NewZimbabwe.com, Harare Mayor Jacob Mafume said this is not a good time to play the blame game.
Mafume however acknowledged that Harare City Council is not solely responsible for the sewer which finds its way to the lake.
"We as the city... Yes, we have work to do in terms of raw sewage issues.
"However industry and other informal settlements and other poachers around the area are contributing to the degradation of the quality of water at Lake Chivero.
"It needs all stakeholders' approach to look at the number of activities that are happening around that area.
"At this point, we need to stop finger-pointing, we need to find a solution.
"The lake has been polluted over time and therefore it is very critical for us to quickly find a solution and find resources to deal with the contaminants that are affecting the lake," he said.
Responding to questions on X, Mafume seemed not convinced that cyanobacteria caused the deaths of white rhinos.
"As someone who has worked in the criminal justice system. The story is about a bacteria that targets four white rhinos and fish? Do we really need a Sherlock Holmes on this one? Gentlemen four rhinos have died, who killed them? Lake chivero! Really! Yes water is green and some fish died," he wrote.
Mafume said they are currently treating their sewer through the waterworks department and also sourcing funds from the government to deal with these issues.
In a statement issued Monday, Harare City Council said teams are already on the ground to take samples from the particular part of the lake the rhinos drink from.
Lake Chivero is abundant in various fish species, including tilapia and catfish.
A number of registered fishing cooperatives and unregistered individual fishermen operate at the lake with their market largely being Harare residents.
Lake Chivero Recreational Park accommodates about 400 species.
Meanwhile, according to the World Health Organisation (WHO), Cyanobacterial toxins occur naturally, but human activity influences the extent to which toxic cyanobacteria proliferate.
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WHO recommends management of lakes, reservoirs and rivers to prevent cyanobacterial blooms is critical to protect human health.
The specialised agency of the United Nations responsible for global public health also says marine cyanobacteria can cause severe skin lesions, for which, however, there is still a lack of dose-response information as a basis for estimating tolerable exposure levels.
"Some people may experience allergic reactions to cyanobacteria, whereas others may be unaffected."
People may be exposed to cyanotoxins through oral, respiratory and dermal routes.
Ingestion may occur through drinking water or accidental uptake during water sports, recreational or occupational activities.
In some settings, contaminated food can be a source of dietary exposure.
This includes fish collected from bloom-ridden water bodies.
