Popular walking and mountain biking tracks in Nelson remain closed after dozens of cyanide baits were discovered.
The police believe the baits were laid by someone wanting to kill possums for their fur. Since Tuesday, 79 baits have been found on the Dun Mountain track and others in the Brook Valley.
Nelson City Council staff are still searching in case there are more of the small mounds of cyanide paste.
The Nelson police say whoever laid them could be charged with offences relating to endangering public safety, which carry a prison sentence.