The Department of Environment and Natural Resources (DENR) on Monday asked Davao City Mayor Sebastian "Baste" Duterte to explain a series of waste dumping incidents outside the agency's Region XI office while filing a criminal complaint against the owner of a vehicle allegedly used in one of the incidents.

In a letter dated 15 June, DENR Region XI Regional Executive Director Mercedes Dumagan sought the mayor's clarification after agency personnel intercepted individuals dumping mixed waste in front of the regional office in Lanang.

Dumagan said the regional office is investigating how the incidents occurred while reiterating the importance of proper waste management and compliance with existing regulations.

"We are clarifying how these incidents came about and reiterating the importance of proper waste handling and compliance with established procedures," Dumagan said.

"Our goal is to ensure that waste collection areas are properly designated and consistent with the city's plan," she added.

Initial findings showed that the discarded materials appeared to consist of unsegregated commercial waste, a possible violation of the Ecological Solid Waste Management Act.

The DENR also said it is coordinating with the Philippine National Police to verify the identities of the vehicles involved for documentation and possible legal action.

"We are addressing individual incidents as well, including the vehicle seen on video. These steps help ensure accountability while the city continues to manage the impacts of the landfill suspension," Dumagan said.

The agency noted that Davao City's landfill in Tugbok, New Carmen has remained temporarily closed since the 20 May trash-slide incident that resulted in fatalities.

According to DENR Region XI, Mayor Duterte has been given five days to respond to the agency's letter, with copies furnished to senior DENR officials and the Department of the Interior and Local Government.