The Department of Conservation has gone to the police after several incidents of vehicle tampering, believed to be in relation to 1080 protesting.
Wheel nuts have allegedly been loosened on vehicles in two different regions, and a wheel came off while a contractor was driving.
Director-general Lou Sanson says he believes it's meant to intimidate DoC and OSPRI workers and disrupt aerial pest control operations.
1080 baits have also been left in a letterbox at a DoC address.
Mr Sanson says people have a right to lawful protest, but he won't tolerate anyone putting his staff at risk.
The State Services Commission said there was "absolutely no justification" for the tampering and threats.
"Tampering with the vehicles of DoC staff and contractors puts them, their families and other road users in danger of a serious crash, and putting poison baits in mail boxes of private houses is clearly an attempt to intimidate," said commissioner Peter Hughes.
"This unacceptable behaviour is coming from a very small group of people and is rightly under police investigation."