NAIROBI, Kenya — Kenyan authorities have arrested four people as a multi-agency investigation continues into the deaths of 18 elephants in the Amboseli ecosystem.

The Kenya Wildlife Service said the suspects were apprehended after authorities discovered chemicals believed to be toxic during a search in the Tikondo area of Loitoktok Sub-County.

Preliminary laboratory findings suggest the elephants may have died after ingesting pesticide-contaminated tomatoes, raising the possibility of poisoning. However, wildlife experts have questioned aspects of the theory, and investigators have not established criminal responsibility.

The elephant deaths occurred between June 24 and July 24 across Amboseli National Park, Kimana Sanctuary and Kuku Ranch.

A fifth suspect is reportedly still being sought as investigations continue.

The case has intensified concerns about wildlife protection, pesticide use and human-wildlife conflict in the Amboseli region, which borders Tanzania and is home to one of Kenya's best-known elephant populations.

Authorities are expected to continue forensic investigations before determining whether charges will be brought.