Council officials are investigating after four pet dogs died in the past few weeks after being walked in a country park in Lincolnshire.
North East Lincolnshire Council has asked pet owners to be vigilant after the deaths at Cleethorpes Country Park.
Although officials have not connected the deaths, they are trying to determine the exact cause.
The only common link so far is that they are all regularly walked in the area, a council statement said.
'Early stages'
As a precautionary measure, the council is advising pet owners to keep their animals on leads for the time being, while staff check the area for any potential causes.
The authority has been in touch with local vets regarding the issue, and has urged anyone who has seen anything suspicious to get in touch with the council.
Councillor Andrew De Freitas, the leader of North East Lincolnshire Council, said officials were taking the matter very seriously.
"It must be stressed that this investigation is still in its very early stages and nothing has been found which can confirm these deaths are linked to the park itself," he added.