Properties in the Portland and Heywood areas were searched by wildlife investigators backed by Victoria Police on Tuesday and Wednesday.
Electronic and documentary evidence was seized, Chief Conservation Regulator Kate Gavens said on Thursday, as well as other items including an allegedly unregistered firearm.
Six search warrants have now been executed in south-west Victoria as part of this investigation.
The regulator’s office said its major investigation unit has been investigating the koala deaths, believed to have occurred in late March, since Sunday, February 2, when a crime scene was established at a Cape Bridgewater property.
The Conservation Regulator is still appealing for information with anyone who knows anything encouraged to contact Crime Stoppers.
“Our investigators have collected a number of witness statements and are continuing to seek out new witnesses, who could provide crucial information as part of our investigation,” Ms Gavens said.
“We are appealing to members of the public who may have information about this case to contact CrimeStoppers, as even a small amount of information may lead to significant outcome.”
Anyone with any information should call CrimeStopppers on 1800 333 000.