GABORONE, Botswana — Months after hundreds of elephants were found dead in a concentrated area near Botswana's famed Okavango swamps, raising fears that they had been intentionally poisoned, the southern African country's government said test results on samples collected from the carcasses pointed instead to a naturally occurring toxin produced by cyanobacteria.

The official death toll stands at 330, with the fatalities occurring between late April and June. Botswana has the world’s largest population of elephants, around 130,000. Their growing numbers have been lauded by conservationists, and Bostwana has become a mecca for tourists seeking to witness and photograph wildlife.

Popular sentiment in parts of the country has turned against elephants, however, as many blame them for the destruction of cropland. President Mokgweetsi Masisi campaigned and won reelection partly on promises to keep elephants more in check, and his government has reintroduced a small number of elephant hunting licenses, which were banned under his predecessor.

“There is absolutely no reason to believe that there was human involvement in these mortalities,” Cyril Taolo, the deputy director of Botswana’s Wildlife Ministry, said Monday at a news conference in the capital, Gaborone.

That unequivocal assertion was complicated later in the conference by Mmadi Reuben, the ministry’s head veterinary officer, who said that while cyanobacteria-created toxins had been identified as the culprit, the deaths remained mysterious, especially the question of why only elephants died when the toxin was in water available to other animals.

“We have many questions still to be answered, such as why the elephants only and why that area only. We have a number of hypotheses we are investigating,” Reuben said.

Conservationists working in Botswana have become bitterly divided over the question of human-elephant conflict. Some allege that the government is using, and even fomenting, anti-elephant sentiment as a populist political tool, while others see the government as trying to balance conservation and human needs.

Keith Lindsay, an elephant biologist with 40 years of experience, including five in the Wildlife Ministry before Masisi came to power, said he still believed that the elephants in the Okavango had been “targeted” and claimed that the tests did not rule out other neurotoxins available to farmers. He also called on the government to release the full test results to the public.

The samples were also tested for cyanide, pesticides and anthrax at laboratories in South Africa, Zimbabwe, Canada and the United States. Poaching was ruled out early on because the elephants’ valuable tusks were left untouched.

Another conservationist with decades of experience in Botswana, Map Ives, said the findings were plausible, especially given rising water levels over recent years in the Okavango, which may result in cyanobacteria rising from lower soil levels to the surface.

More than 20 elephants died in neighboring Zimbabwe last month under similar circumstances. Zimbabwe and Botswana have seen growing elephant populations while numbers are on the decline in almost all other African countries.

The spate of deaths ended in late June, coinciding with the drying up of pools of water where cyanobacteria-created toxin contamination would have taken place.

Correction: An earlier version of this story inaccurately referred to cyanobacteria as a toxin. The tested samples pointed to toxins created by cyanobacteria. This story has been updated.

Bearak reported from Addis Ababa, Ethiopia.