The RSPCA has said it has exhausted all leads over the spate of dog deaths in Cross Hills, North Yorkshire.
After many dogs died before having the chance to be given pet medication, the RSPCA launched an investigation to find the cause of their deaths.
However, the charity, which has been investigating the cause since June, has now said it has exhausted all leads.
At least nine dogs died after walking on the footpath off Station Road in Cross Hills. The cause of death was eventually determined as Strychnine, a poison that is used to control population numbers of moles.
Most dogs died within minutes of returning home before they could be taken to the vet.
RSPCA chief inspector Beth Clements, who oversaw the investigation, said: "We simply have nowhere else to go with this investigation.
"With a heavy heart, I have to say that we have fully exhausted all lines of enquiry and the investigation is, as such, now closed.
"Of course, should any specific information come to light we will look to reopen it."