Dodoma - Tanzania's natural resources minister accuses police of "dilly-dallying" and failing to arrest key suspects in last year's killing of a prominent South African wildlife conservationist, Wayne Lotter.
Hamisi Kigwangalla claimed on Thursday that police had the information "but had failed to take action" against those who planned the killing. He threatens to take the matter to President John Magufuli.
Lotter, who developed techniques to catch elephant poachers and ivory smugglers, was shot and killed in Tanzania's commercial hub, Dar es Salaam.
The city's Special Zone Police Commander Lazaro Mambosasa says the investigation continues.
Kigwangalla also is releasing a list of suspects in a large wildlife trafficking ring that has operated in the country for decades. They are accused of using their hunting licenses to orchestrate with a syndicate of elephant poachers.