Unacceptable levels of arsenic in the drinking water drawn from rural wells near the small community of Vanderhoof have prompted a warning from officials with the Northern Health Authority.

Officials say people should test their well water, and stop drinking it if the arsenic levels are too high.

Tests showed higher-than-acceptable levels of arsenic in the well water of 20 homes on the north side of Vanderhoof, with some wells showing twice the acceptable level.

The amount of arsenic that's been found would have been acceptable up until last summer. That's when Health Canada tightened its regulations, bringing Canadian water standards into line with those recommended by the World Health Organization.

The Canadian cut-off used to be .025 mg/litre of arsenic. Last year, that was reduced to .010 mg/litre, which is the international standard.

Some of the wells in the Vanderhoof area, which is about 100 kilometres west of Prince George, have been found to have up to .020 mg/litre of arsenic in the water.

Arsenic is a naturally occurring element. But long-term exposure to high levels of arsenic is a cancer risk.

Officials also say there have been "elevated" arsenic levels in several other locations in the region.