Honduran police have arrested four people in connection with the killing of environmental and Indigenous rights activist Berta Caceres, including an employee of a company whose project she helped block, the attorney general's office says.
Caceres, 43, who fought to stop the construction of hydroelectric plants and mines on Indigenous territory, was fatally shot in La Esperanza, Honduras, in early March, sparking domestic and international outrage.
One suspect was a man working for Desarrollos Energeticos, or DESA, a local firm behind the Agua Zarca hydroelectric project that Caceres managed to bring to a halt after mobilising residents and activists, the attorney general's office said.
Hidroelectrica Agua Zarca, a unit of DESA, said in a statement on Monday it was surprised that the man, identified as Sergio Rodriguez, had been arrested and that it had no "material nor intellectual" connection with the killing of Caceres.
It described Rodriguez as a manager working in social and environmental issues.
The company added it had been co-operating with authorities in their inquiries since the outset.
Two of the other suspects were soldiers, one on active duty and the other now retired, a spokesman for the armed forces, Lenin Gonzalez, told reporters.
Honduran President Juan Orlando Hernandez congratulated the investigators and reiterated his pledge to see justice served.
But prosecutors have yet to put forward an official explanation for what motivated the killing.
Caceres, who had previously received death threats, won the Goldman Environmental Prize in 2015 for her efforts to prevent the construction of a $US50 million dam that threatened to displace hundreds of Indigenous people.