It is believed, but not confirmed, that one dog has died and another has received vetinary treatment after an adder bit them at the popular rambling spot.
Wakefield Council said it has received no reports of a dog being bitten by a snake at the park.
Glynn Humphries, service director for Environment and Streetscene, said: “No-one has reported any incidents to us about their dog being bitten by a snake at Newmillerdam.”
He added that pet owners should get in touch if they want to report something that has happened to their dog (see below).
But online reports have surfaced on social networking site Streelife, which allows discussions between people who use the same public places.
On a page for people who walk at Newmillerdam, member Sally M posted: “Just had this news from a dog walking friend: I just wanted to let you know that my dog walking buddy has a friend whose dog has been bitten by a snake and died.
“Another has been bitten (bigger dog) and was very ill at the vet but seems to be OK. Just don’t let your dog into any deep leaves, undergrowth and pass it on.”
Site member Claire Gelder said that a vet had told the dog owner that its injuries were consistent with a snake bite.
Dog walking business Wakefield Pet Care warned visitors to the park to keep their pets close.
They said: “There has been reports of two incidents regarding the possibility of adders at Newmillerdam. Unfortunately one dog has passed away and the other is currently receiving veterinary care.
“Adders usually aren’t present until early April but they appear to have come out earlier this year.
“Please exercise caution in these areas. Adders use biting as a last resort of defence from threat usually because of being stepped on, trapped or handled.
“Keep dogs close if off lead but it would be more preferable to keep them on leads.”
The company later added: “Newmillerdam is a fantastic piece of land to walk along and we’d never discourage people from visiting.”
If something has happened to your dog, contact the council on 0345 8 506 506.