– It has not been possible to prove that they were involved prosecutor Anna Nilsson told SVT Nyheter Västerbotten.
Suspicions against the fourth individual remain, and the prosecutor hopes to press charges before the summer, according to SVT Nyheter.
The incident occurred in early February when three reindeer were discovered dead in Kullaskogen outside Umeå.
The National Veterinary Institute (SVA) confirmed they died from blunt force trauma and cuts to the throat. Their bodies were found the same week a stage of the World Rally Championship event, Rally Sweden, was held nearby.
The incident gained widespread attention after a video was published on social media, reportedly showing the reindeer being abused and run over.