Approximately 400 fish carcases have been found in a Donegal river this week.

An investigation was launched on Tuesday 25 June after Loughs Agency discovered pollution on the St Johnston Burn.

A pollutive substance, the environment agency said, was clearly visible in the river and statutory samples were taken for analysis.

Loughs Agency has estimated that 7km of the watercourse has been affected and substantial fish mortalities were discovered, with approximately 400 fish carcases collected to date.

It is anticipated that this figure will rise in the coming days.

Investigations are continuing into the cause of this incident, but fishery officers are confident that they have identified the source.

Resources from Loughs Agency will be at the site of the incident until the investigation is complete.

Anyone who discovers a dead fish in the area is asked to leave it and contact Loughs Agency directly on +44 (0) 28 71 342100 to arrange collection with a fishery officer.

Loughs Agency has confirmed that a further update will be provided in due course.