An investigation has been launched after fears that contaminated water could have leaked from a landfill site onto a protected nature reserve near Poole.

It is believed the leachate – water mixed with decaying waste in the soil – which could contain ammonia, escaped onto Upton Heath from the Beacon Hill landfill site at Corfe Mullen.

The Environment Agency is investigating after a resident alerted Dorset Wildlife Trust, which manages the 110-hectare Site of Special Scientific Interest, to the smelly water which spread across a bridleway onto heathland.

The protected site is home to all six species of British reptile, which are just starting to emerge from hibernation, as well as the insects they eat and threatened birds, such as the Dartford warbler.

However a spokesman for SITA UK, which owns the landfill site, said there was no risk to the public or wildlife from the incident last Friday night.

“There was an allegation that some type of contaminated water had leaked out from the Beacon Hill landfill site,” said Paul Gaimey, Environment Agency media relations manager.

“We are investigating to see what the cause was and how it happened,” he said.

He added: “Some people might see this bright orange liquid and be alarmed that it looks like contamination.

“That is naturally occurring iron mould. People might assume that’s the contamination, it’s not.”

Mike Dobson, regional communications manager for SITA said: “We are aware of the possibility that some surface water contaminated by leachate may have inadvertently diverted from our Beacon Hill landfill site onto adjacent heathland.

“The EA are investigating the incident and we are co-operating fully with them and await their report.

“We have taken immediate steps to ensure that as per normal practice, only clean surface water is piped away from our site.

“Leachate will continue to be treated separately at our onsite plant.

“Given the short time frame involved there would have been no danger whatsoever to the public,” he said.