A major fishing and camping site near the Blue Mountains has been closed indefinitely after reports of a significant fish kill.

The Lithgow City Council has closed Lake Wallace at Wallerawang after reports of a significant number of dead redfin.

Redfin, also known as European perch, are an introduced pest in Australian waterways but also a popular angling fish.

The Lithgow City Council is urging visitors to avoid the lake while the investigation is ongoing.

The Wallerawang Acclimatisation Society, which assists with fish stocking in the local area, said it was too early to tell what had caused the mass die-off.

“At the moment we don’t have a huge amount of information, it seems to be only affecting the redfin population,” treasurer Nathan Turner said.

He said it was potentially epizootic haematopoietic necrosis (EHN) virus, which is known to affect redfin and can also spread to native Australian fish.

The federal Department of Agriculture said EHN virus could also affect Macquarie perch and rainbow trout.

The virus was known to cause mass deaths for several weeks in summer months and then disappear for years, the department said.

Mr Turner said redfin were a terrible pest in Australian waterways but the cause needed to investigated because it could be a symptom of a wider problem with the habitat.

“They’re as bad for the waterways as carp. They take over the waterways; they breed voraciously.

“But we’ve got to see what the cause is and what the outcome may be.”

Lake Wallace is a popular camping and recreation area that sits on the Cox’s River at Wallerawang and was originally created to supply water to local coal-fired power stations.

Mr Turner said locals had reported seeing up to 50 and 100 dead redfin at a time at the lake.