NAIROBI, Kenya (AP) — Fifteen elephants that died over the past month in southern Kenya are suspected to have been poisoned by tomatoes contaminated by cyanide, wildlife authorities told local media Wednesday.

Authorities did not say who they suspected in the contamination of tomatoes from farms neighboring the Amboseli National Park. In the past farmers have been suspected of deliberately poisoning elephants to prevent them from eating crops.

The park in southern Kenya borders an area where farming and the raising of livestock are prevalent.

Kenya Wildlife Service Director General Erustus Kanga said preliminary laboratory tests detected cyanide. “Cyanide is a highly toxic chemical, particularly for elephants,” Kanga told local media.

The Kenya Wildlife Service warned that the contamination could have wider consequences because livestock also graze in the area.

“Other than the elephants and the wildlife that may be feeding in those fields, we have the local livestock. We have the goats. We have the cattle that are there. Eventually, if this is truly what is in the system, then we are going to see a bigger impact,” Kanga said.

Wildlife authorities said the toxic substances found in the deceased elephants pose no immediate threat to human health.