Out of 900 samples tested from a major Canadian river polluted by an oil spill last month, five exceeded drinking water guidelines, officials said on Wednesday, cautioning it was unclear when the river would be safe to drink from again.
The July 20 leak from a Husky Energy Inc pipeline into the North Saskatchewan River has forced tens of thousands to find other sources of drinking water, including the western Canadian cities of Prince Albert and North Battleford.
The water tests were conducted by a group including government and Husky officials and independent experts.
All of the samples that exceeded guidelines were found within 20 kilometers (12 miles) of the spill, and none have exceeded guidelines since July 24.
"That would suggest there is not an ongoing issue, which is fairly expected," said Paul Nony, a senior toxicologist at Arkansas consulting firm Center for Toxicology and Environmental Health.
Oil doesn't mix well with water, but typically clings to organic material or the shoreline, Nony noted, adding that "we're not seeing any surprises."
However, more testing, monitoring and a formal risk assessment study are necessary before the river can be used as a drinking water source, said Patrick Boyle, spokesman for the Saskatchewan Water Security Agency.
Samples were collected on the river's surface and at different depths, down to its bottom. A separate study will examine the spill's impact on aquatic life.
On Tuesday, Reuters reported that the spill was the third in the same area in eight months, according to government records. The failed pipeline had not been inspected by Saskatchewan's energy regulator since it was constructed 19 years ago.
Asked about the findings, Saskatchewan Premier Brad Wall said his government has been working to bolster regulation.
"There is a requirement too that companies provide that inspection and that oversight, and you know we're going to do an investigation into this," said Wall. "We're going to find out answers to questions like that."
(Reporting by Rod Nickel in Winnipeg, Manitoba, with additional reporting by Allison Martell; Editing by Jeffrey Hodgson and Sandra Maler)