A dog died and another became seriously ill after being walked in Green Park in Ossett.
The original news about the police investigation was revealed on Monday as West Yorkshire Police officers said that the force was investigating reports from members of the public.Hundreds of people shared the appeal on Facebook to warn other dog owners about the issue.
Michelle Karasiewicz said: "Poor dog, RIP, and hope other dog gets well very soon. Evil lowlifes that have nothing better to do but cause suffering to animals and the owners."
Local Ossett resident David Clay said: "We were appalled and engraged that anyone would want to poison dogs in our area.
"We walk our Yorkshire terrier almost every day in Green Park and the previous dog was also walked here.
"We've done 25 years of dog walking without anything like this.
"After hearing of these horrendous poisionings we now keep our dog firmly on his lead which is a shame and restricts his exercise.
"We will continue to do this until this spate of incidents has gone.
"Green Park is a traditional park that leads onto Southdale Playing Fields.
"It is extremely popular not only with dog walkers but also with many sports teams both adult and junior.
"The dog footfall (or pawfall) in this park must be very large."
The news follows a series of reports of Parvovirus in Leeds, which in one case proved fatal, although it is not thought to be connected.