The Mogale City local municipality has launched an investigation into a series of spillages of human excrement in the Cradle of Humankind.

Human waste has been spilling on to roads on the West Rand for several weeks while it is being transported in open trucks and trailers by a Durban-based company Aqua Bulk from the Zuurfontein informal settlement to farms in the Tarlton area, through the Cradle of Humankind.

The investigation into the spillages was launched following a media inquiry by The Sunday Independent, with the Mogale municipality expressing "extreme concern" about the risks posed to motorists and to the health of the community.

Colleen Mes, a DA city councillor, last week said the party would take up the matter with the municipality.

Mes, who lives along the route taken by the trucks through the Cradle of Humankind, said waste had been "plopping out of the trucks" for several weeks.

On March 30, a large amount of waste spilled over the sides of an Aqua Bulk truck at the intersection of the Sterkfontein road and the R563 to Hekpoort. A thick layer of excrement lay strewn across the road for several hours before the bulk of it was removed and the remainder swept to the side. On Tuesday there was a similar, but smaller, spill near the traffic circle.

Mes, whose main concern was the health risk the raw waste posed to local residents, said it was being transported to Tarlton to be dumped in sludge dams.

"We have not yet established where these places are, but we are working on it," she said. "The route that these trucks have been taking goes right through the Cradle - there are school children walking these routes and parents have complained that they get stuck behind the trucks while the stuff is slopping out of the open trucks all over cars and the roads."

Nkosana Zali, a Mogale City spokesperson, said the municipality had been unaware human waste was being transported in open trucks. This violated by-laws, he said: "It is prohibited to transport sewage in an open truck."

Zali said the municipality had entered into a three-year contract with a company called Aquatech to desludge septic tanks, pit latrines and conservancy tanks in areas within its jurisdiction. In terms of the agreement, "this waste is transported by means of an enclosed vacuum-tank truck".

The responsible department "is now investigating this allegation fully, because it is the first time that we learn of it", Zali said. Had it known about the problem earlier, it would have taken immediate action, as the municipality would "not insult the world by spitting on a World Heritage site".

Aqua Bulk could not be reached for comment last week.