Cameco Corporation, the company that owns a shutdown nuclear processing plant in Port Hope, said contaminants may have leached into Lake Ontario.

One of its plants was shut down last July after it discovered contaminants in the soil and in groundwater.

Cameco said computer models suggest the uranium and arsenic that were found in the soil beneath its plant have reached the harbour at Port Hope, about 100 kilometres east of Toronto.

However, company spokesman Lyle Krahn said tests on lake water are not showing an increase in contaminants.

"It's possible that very small amounts of [uranium and arsenic] are going into the harbour," said Krahn.

The company has been testing the water for nine years, said Krahn, and has seen "no noticeable change in the water."

Cameco suspended operations at the plant last July after uranium was found in the soil during construction. But the company also said it's been testing lake water around the plant and there's been no change in the quality.

Cameco said it has presented its findings to the Canadian Nuclear Safety Commission, which oversees companies that process radioactive material.

The commission said the seepage is considered low risk.

The town of Port Hope said there's no concern over the town's drinking water. Town council has been told there are no health or safety issues.

The company said it's collecting and treating the groundwater.

Cameco said it should have a better idea about what contaminants are reaching the lake through the groundwater once it digs a couple of dozen wells along the harbour in Port Hope.