Officers from the Scottish Environment Protection Agency (SEPA) have been informed by Scottish Water of an ongoing incident at the Castlehill Water Treatment Works at Glendevon.
An incident occurred with the same site at the beginning of last week, but the latest incident is thought to be unrelated.
SEPA has been monitoring the situation over the weekend and is currently monitoring the actions taken by Scottish Water to rectify the problem in order to ensure there is minimal impact on the environment and human health.
Scottish Water has not yet published any official statement on the situation.