The RSPCA has closed its investigation into the deaths of at least nine dogs in Cross Hills, North Yorkshire after exhausting all lines of enquiry.

In May, the charity urged members of the public to avoid taking their dogs to a footpath off Station Road, Cross Hills after a number of dogs fell ill and died after being walked there.

The dogs died within minutes of returning home, in many cases before their owners were even able to get them to the vet.

Test results eliminated naturally occurring poisons like blue-green algae and post-mortem results were initially inconclusive but eventually a poison called Strychnine was found to be the cause. The substance was used for the control of moles until it was removed from legal sale in 2006. Its use was banned on anything other than moles in 1963.

Despite the amount of information we received from concerned members of the public we were unable to locate the source of the Strychnine.

RSPCA chief inspector Beth Clements has overseen the investigation and said: “Despite our best efforts and the best efforts of all of the organisations and individuals involved we simply have nowhere else to go with this investigation.

“I would like to say thank you to each of them – North Yorkshire Police, Craven District Council, The Environment Agency, Natural England, RSPCA Craven & Upper Wharfdale branch and of course the veterinary practices and owners.

“The co-operation of the media and dog lovers who helped spread the message on social media played a crucial part in ensuring more pets weren’t affected and I’d like to thank them also.

“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 re-open it but our investigation is no longer ongoing.”