Radiation was found in materials transported from the Robert Pickard Environmental Centre, the City of Ottawa said.

Low-level radiation has been found in sludge from the City of Ottawa's wastewater treatment plant.

Waste material taken from the Robert O. Pickard Environmental Centre, being transported to the United States for disposal, was turned back when it was tested at the border.

According to the city, the material consisted of isolated biosolids, which were discovered to be radioactive last Thursday.

Dixon Weir, the director of Ottawa's water and wastewater services branch, said the biosolids were turned back at the border because "a very low level of radioactivity had been identified in those loads."

The city, however, stressed that tests indicate drinking water remains safe.

A hazardous-materials team has been called in to investigate where the radiation at the wastewater treatment plant came from.

The city said it doesn't think there is a link between the radiation in the materials from the sewage treatment plant and a Dec. 5 leak at the Chalk River nuclear plant 185 kilometres northwest of Ottawa.

For now, the loads of material are being kept at a site in Iroquois, Ont., a border town near Cornwall.

Consultants from Toronto will arrive to conduct more intensive tests Wednesday and hope to know more about the origin of the radiation by Friday.