A family has been left heartbroken after one of their dogs is believed to have ingested cyanide on a walk.

Alfie Penfold was walking his three Labradors at the Sunken Gardens park in Margate when nine-year-old Bentley suddenly became limp.

He had taken the dogs out on Monday for the same route they walk every day and nothing was out of the ordinary. They were running around a green area and Bentley was foraging in a bush.

When Mr Penfold started walking home with the three animals, Bentley suddenly collapsed.

"I am absolutely heartbroken about the untimely death of my Bentley boo," he said.

"Everyone should stay extremely vigilant when walking their dogs. They should all hold their dogs a little bit tighter as you never know when it could be your last.

"I am very keen to get some justice as I don't want my lovely boy's death to be in vain, if his death means other dogs lives will be saved then it will mean something."

Alfie's sister Ellie says the vets think Bentley ingested cyanide but do not know where the poisonous material has come from or if it was deliberately laid for gardening purposes or in more sinister circumstances.

"He was a really healthy dog," she said. "He went out happy in the morning for his walk and within 45 minutes they were doing CPR in the vets and he did not make it.

"When I got to him he just looked at me and flopped into my arms.

"I thought as soon as he would have seen me he would have lit up because that is what always happens when I visit him, he was always happy to see me.

"He collapsed on to the vets table and his gums had gone bright blue. They asked if he had eaten any garlic or onions because they are poisonous to dogs but he had not, we are really careful with what we feed them. He is a very good dog and does not pick food up unless he is allowed it, if there was a plate of chicken in front of him he would not take it."

Bentley was put on oxygen and an intravenuous drip at Vets Now emergency vet in Herne Bay. The plan was for him to stay overnight and the family to collect him the next day.

"He was completely cold, his gums were blue and his stools were bright red but not with blood," Miss Penfold said.

"We went back to my house which is only six minutes away from the vet.

"As we pulled up on the drive they called us to say he was dead.

"We rushed back and the vet said it was not onion or garlic, it was something that had poisoned his system and there was no way that onion or garlic would do that.

'From the moment he got home limp to being in the vets and declared dead, it was 45 minutes...'

"They think something had been intentionally laid because of the strength and the volume of it in his system.

"The vets confirmed it was cyanide and a high volume of it because it is the only thing that can kill that quick."

Miss Penfold posted about what happened on Facebook to warn other dog owners, and found out the same thing had happened to another dog.

"A few people had commented someone else's dog has died of cyanide poisoning after walking in the same location on the same day," she said.

"It is the same route my brother takes everyday and I have no idea why it would be put there."

The family has been left heartbroken after losing their beloved pet so suddenly.

"He was my pride and joy," Miss Penfold said.

"I loved him so much. It is a massive shock for my brother too.

"I have recently moved out and Bentley has been living in my brother's room.

"We all love him so much and now we have had to come home without him."

'If we get justice for Bentley then he hasn't died in vain...'

The family has contacted Thanet District Council (TDC), the police and the Sunken Gardens committee about the incident.

A police spokesman said inquiries are ongoing to establish the circumstances of Bentley's death.

The Sunken Gardens Committee posted on Facebook about the incident yesterday to say they are helping police with their inquiries.

"The Sunken Gardeners are very sad to hear that a beloved dog has passed away from allegedly ingesting cyanide around the garden," the post read.

"We have been in the garden this morning [Tuesday] looking for any signs of the poison, but not found anything untoward.

"We are helping police with their inquiries and have reported the incident the the council's environmental service department.

"Until a toxicology report has been issued we won't know if it is cyanide, if it was in a condensed poison, or if the Labrador maybe ate a discarded peach/apricot stone. Sending condolences to the bereaved family."

A TDC spokesperson said: "We would like to extend our deepest sympathies to the owners of the dog following this tragic incident.

"The event has been reported to Kent Police who have confirmed that enquiries are ongoing to establish the circumstances of the death."

Cyanide is used to make paper, textiles, and plastics as well as chemicals used to develop photographs.

Cyanide salts are used in metallurgy for electroplating, metal cleaning, and removing gold from its ore. Cyanide gas is used to exterminate pests and vermin in ships and buildings.

It can also be used to deter mammals and insects from eating plant seeds while it is also present in some common plants such as rowan buds.

A spokesperson for Vets Now Herne Bay said: “A dog was brought to our out-of-hours pet emergency clinic in Herne Bay this week.

"Our dedicated emergency team worked diligently to try and save his life, but unfortunately he arrived extremely unwell and he sadly passed away.

"Our thoughts and sincerest sympathies are with his family at this difficult time.”