A puppy died in his owners arms just seconds after swallowing heroin dumped in woodland.
Nine-month-old cocker spaniel Wilfred died after eating black tar heroin, an impure opiate, while out for a walk.
Owner Nick Dinsdale said he is totally devastated and police have issued a warning to the public about keeping an eye on pets and children.
Nick said: We went down to the woods for a walk.
Halfway round he was just bouncing about, having fun.
We get to the middle of the woods. He came back towards me and I carried on walking.
I look about 30 feet back and he is sat down. I thought that was unusual. I could see something was seriously wrong.
Within 20 or 30 seconds he just keeled over. I thought has he got something stuck in his mouth. There was brown on his tongue.
He just died on me. He died in my arms. He died within a minute of me turning back after it happened.
Nick, 50, and wife Gina, of North Killingholme, Lincolnshire, bought Wilfred for £750 when he was eight weeks old.
Determined to find answers, the pair paid for a post mortem to uncover the cause of Wilfreds sudden death on Thursday.
Tests revealed he had ingested black tar heroin, a form of heroin that is sticky like tar or hard like coal during his walk in Habrough Woods.
Veterinary surgeon Jacqueline Buck, from Grimsby-based Abbey Vet Centre, said: We feel that local people need to be made aware of this incident in the public interest because neither dogs nor children should be roaming the area free because of the danger to their life and health if they were to come into contact with similar illegal substances.
Humberside Police said they are investigating and added: We would advise dog owners to be vigilant about what your dog is picking up when out on walks.
If you have any information that may assist our enquiries please get in touch by calling our non-emergency number 101 quoting log number 352 of 06/12/18 or Crimestoppers anonymously on 0800 555 111.