The Schiedam mystery: six dogs died after walks in parks, with poisonous mushrooms and contaminated soil ruled out — what investigators are checking and how to keep your dog safe

What happened

On 29 October 2026 the city council of Schiedam, near Rotterdam in the province of South Holland, announced the first results of an investigation that has been under way since late September. In that time, six dogs that had been walked in the city's parks have died. Five of them were walked in De Plantage park and the sixth in Beatrixpark. According to the council, all the dogs had the same symptoms.

The main finding of the first tests is that the dogs almost certainly didn't die from poisonous mushrooms, and the soil in the park isn't contaminated. This was one of the main theories, and it can now be set aside.

How it began

The first cases came in the last days of September. On 29 September the national broadcaster NOS and regional station Rijnmond reported on four dogs that had died within days of walks in De Plantage. A local woman described walking her dachshund there and meeting her neighbour in tears: her dog Buddy had eaten something in the park, started vomiting heavily with blood and died a few hours later. At the clinic, the neighbour was told that another dog walked in the same park had died that day.

According to owners, other dogs also fell ill after walks. The police became involved and began checking for signs of a crime, and signs went up in the park: "Possibly poison. Watch your child and pet!"

What the authorities did

The police and council investigated together. As early as 2 October, part of De Plantage — a rose garden of several dozen metres — was dug out and the soil taken away in containers. The council explained that it was doing this as a precaution at the request of the police, and would return the soil if it proved clean.

On 5 October a sixth dead dog came to light. It had never been walked in De Plantage, only in Beatrixpark. After that, soil tests began in the second park too, and large parts of it were cordoned off. Dog owners were advised to walk their pets elsewhere.

What the first tests showed

On 29 October the council reported that the first soil tests had found no contamination and that the poisonous mushroom theory could be dropped. But the investigation isn't over:

• investigators are checking whether plant bulbs were in the park — some are dangerous to dogs;
• the Netherlands Forensic Institute (NFI) is carrying out a forensic examination.

The council hasn't yet said when the results will be ready.

We know that the people of Schiedam are very worried, and we're doing everything we can to get results as quickly as possible. As soon as we know more, we'll let you know.

Schiedam city council

Why bulbs are being checked

Autumn is when tulips, daffodils, hyacinths and other spring flower bulbs are planted in parks and gardens. They're dangerous to dogs: bulbs contain substances that cause vomiting, drooling and diarrhoea and, in large amounts, heart problems. A dog can dig up a freshly planted bulb or pick up one lying on the surface. This is one theory, but only a theory for now: what the dogs in Schiedam ate hasn't been established.

Why forensic experts are involved

If tests find no natural cause — mushrooms, plants, contamination — the question remains whether someone deliberately poisoned the dogs. Such cases do occur in Europe: baits containing poison or sharp objects are found in parks. So from the outset the police have been checking for a crime, and the forensic examination should show what substance was in the bodies of the dead dogs.

Signs of poisoning in dogs

Owners of the dogs in Schiedam saw heavy vomiting, sometimes with blood. In general, a poisoned dog may show:

• vomiting and diarrhoea, including with blood;
• heavy drooling;
• lethargy, weakness and an unsteady walk;
• trembling and seizures;
• rapid or laboured breathing;
• pale or, on the contrary, bright red gums.

Some poisons act within hours, others after a day or two.

What to do if your dog eats something on a walk

1. Call your vet straight away — don't wait for signs to appear.
2. Don't make your dog sick unless your vet says so: with some substances it's dangerous.
3. Take the remains of what your dog ate, or photograph the spot — it can help work out the cause.
4. Note the time of the walk and what you saw.
5. Tell the police or council if you suspect poison was left deliberately.

How to make walks safer

You can't eliminate the risk entirely, but you can reduce it considerably:

• teach your dog a "leave it" command and don't let them pick things up from the ground;
• keep your dog on a lead where there have been poisonings;
• for dogs that pick up everything, a basket muzzle is suitable, as they can drink and pant in it;
• look out for warning signs and council notices;
• in autumn, steer clear of fresh flower beds and places where bulbs have been planted.

What else is dangerous for dogs in autumn

Autumn walks bring a few particular dangers worth knowing about, even if no one in your area has been poisoning dogs:

• mushrooms — most aren't dangerous, but some, such as the death cap, are deadly; you can't explain the difference to a dog, so it's best not to let them eat any;
• acorns and conkers — can cause vomiting, diarrhoea and intestinal blockage, and acorns in large amounts damage the kidneys;
• flower bulbs — tulips, daffodils, hyacinths and crocuses;
• yew — an evergreen often found in parks, with very poisonous needles and seeds;
• antifreeze — sweet-tasting; drips in car parks and on roads attract dogs and cause severe kidney damage.

Rodent poison: a delayed danger

In autumn rodents look for warm places, and people put down poison more often. Many of these products interfere with blood clotting, and signs appear not straight away but after a few days: lethargy, pale gums, bleeding from the nose or gums, blood in urine or faeces, bruising and laboured breathing. So if you've seen your dog eat poison, don't wait for symptoms: your vet can start treatment at once, before bleeding begins. Take the packet or a photo of the product with you.

How to spot a suspicious bait

Baits containing poison or sharp objects most often look like pieces of sausage, meat or bread, sometimes with tablets, granules, needles or bits of glass in them. They're left on lawns, by benches and along paths where dogs often walk. If you find one, don't touch it with bare hands, photograph it, tell the police and warn other owners in the area.

What owners in other countries need to know

The Schiedam case isn't unique: reports of dogs dying after walks in particular places come up from time to time in different European countries. Sometimes the cause is poisonous plants or mushrooms, sometimes blue-green algae in water, and sometimes deliberately laid baits. If several dogs have died in your area, tell your vet, the police and the council: this helps find the source faster and warn other owners. In the Netherlands, cruelty to animals and suspected poisoning can be reported on 144, the animal helpline linked to the police. In the UK such reports go to the police and the RSPCA or Scottish SPCA.

If your dog dies suddenly

This is a hard moment, but a few steps can help you understand the cause and protect other dogs. Ask your vet for a post-mortem and toxicology test: without them the cause of poisoning often can't be established. Write down where and when your dog was walked, what they might have eaten and what signs they had. If you suspect poisoning, tell the police and council and warn other owners in the area. It was owners' reports that allowed Schiedam to link several cases quickly and start an investigation.

What happens next

Schiedam city council has promised to report the results as soon as they're available. Until the examinations are finished, the authorities aren't drawing conclusions, and dog owners in the city remain on alert. Any information is important to the investigation: back in September, the police asked residents to photograph anything suspicious in the parks and report it.

When to see a vet

If your dog starts vomiting after a walk, especially with blood, or has diarrhoea, drools, seems weak, trembles or has seizures, call your vet or go to an emergency clinic immediately. With suspected poisoning, hours count: the earlier treatment starts, the better the chance of saving your dog. If you can, bring what your dog ate, a sample of vomit or a photo, as this will speed up diagnosis.