The Strelitzia Dam in Uitenhage is set to be closed following the discovery of three mortars in its waters over the weekend.
Eastern Cape police have deactivated the projectiles that were found in the dam and warned residents not to pick up unknown objects found in the vicinity of or in the dam.
Two of the mortars were found on Friday while the third one was discovered on Saturday.
Police spokesperson Captain Gerda Swart said the explosives do not belong to the South African National Defence Force.
The police are investigating where the explosives came from and why and how they ended up in the dam.
Swart said the police were consulting with the local municipality to close the dam so that a thorough search could be conducted by the bomb disposal unit to ensure that all the mortars were retrieved.
She warned the public not to pick up or handle any foreign objects they found at the dam.
"Two people found two old mortars in the dam on Friday not realising that they could be fatal. It was later discovered that the mortars were in fact still live and could have exploded. The bomb disposal unit from Port Elizabeth were informed and they were deactivated," said Swart.
She added that on Saturday, a man who was fishing in the dam found a third live mortar.
The man also unknowingly handled it.
"Fortunately, he notified the police and the bomb disposal unit was immediately summoned to the scene and took possession of it. The dam levels have fallen over the last few months and it is believed that this could be the reason for the recent discoveries.
"The police are advising the public that should they stumble upon anything strange or anything that resembles a mortar not to handle or pick it up, and instead to immediately contact the Uitenhage police. When they are mishandled these mortars can detonate which can prove deadly," Swart said.