Interior Health Authority is advising people not to swim at a popular Shuswap beach after a water sample came up with alarmingly high e-coli numbers.

A sign on the roadway at Blind Bay's main beach, across from the community hall, warns people the water quality for recreation is poor and swimming is not recommended.

But it will be several more days before another sample will determine whether there is real cause for alarm.

Dan Ferguson, assistant director of health protection for IHA, said Wednesday the sample found a 3,000-unit count for e-coli, an indicator of potential virus, bacteria or pathogen.

"Because it's 3,000 we're taking the precautionary principle."

Risks are greatest to the young or elderly, who may have weak immune systems. A range of gastro-intestinal illness may result from swallowing lake water while swimming, Ferguson said.

Previous counts have ranged from zero to 100 on the test. But Ferguson said the 3,000 count may be an oddity.

Possible explanations include waves churning up sediment, and concentrating material and the presence of geese feces in the water.

South Shuswap resident Ray Nadeau, a water conservation activist, said the closure is alarming for those in the community. It's a first time anyone can remember a closure at the beach.

"We don't know where it's coming from. We need to find out," said Nadeau, who is sceptical of the geese explanation.

Ferguson said another sample was taken at the beach earlier this week. Results will be known by Monday.