The City of Moncton has had to close the reservoir at the Irishtown Nature Park to all recreational uses due to the presence of blue-green algae again.
Blue-green algae, which is not actually an algae, but rather a potentially toxic bacteria called cyanobacteria, is collecting along the banks of the popular water hole.
It can cause skin and eye infections, liver damage, gastroenteritis, sickness and, at times, death.
City officials will continue to monitor the situation and advise when the ban is lifted, a statement issued on Wednesday says.
Meanwhile, pet owners are also urged to not let their animals drink or swim in the water.
"The City of Moncton apologizes for any inconveniences, and wishes to thank users of the park for their co-operation to ensure visitor safety," the statement says.
The Irishtown reservoir has had ongoing problems with algae blooms in recent years.
"The City of Moncton in partnership with the University de Moncton have been involved in an extensive research project for over 4 years now in developing protocols and conducting water and sediment samples to deal with this issue," the statement says.
The reservoir is the oldest in the city, but is only used now for recreation and is surrounded by popular walking trails.