Toxic blue-green algae is present in a scenic south Armagh lake, the NI Environment Agency (NIEA) has confirmed.
The slipway at the beauty spot has been closed as a result.
The Council said people should abide by any warning notices positioned around the lough.
It advised the public not to drink the water, not to not enter or swim in it, not to use it for recreational water sports, not to let dogs or livestock near the water and not to fish or eat fish caught recreationally from the lough.
It comes as the situation on Lough Neagh worsens.
Earlier this week, the NIEA confirmed that there have been 168 confirmed reports of toxic blue-green algae in Northern Ireland’s waterways since May.
The algae growth is linked to excess nutrients in the water.
Nitrogen and phosphorus from agricultural fertiliser running off fields is believed to be a major contributory factor.
The deaths of birds and dogs have been linked to the recent algae blooms and a number of water-based businesses on Lough Neagh have also had to stop operating.