Alberta's senior medical officer of health says he doesn't know why drinking water in the hamlet of Fawcett has higher than acceptable levels of nitrate.

Alberta Health Services issued a water advisory for the commununity 140 kilometres north of Edmonton on Wednesday.

Dr. Gerry Predy told CBC News Friday that the province doesn't know where the nitrate is coming from or how it's getting into the system.

The government is working with municipal and Alberta Environment officials to restore the system as soon as possible, he said.

"We'll have to work with the municipality over the next little while to determine [the source of the high levels] and do some more testing," Predy said.

In the meantime, officials are warning pregnant women, nursing mothers and parents with infants under six months to stop drinking tap water.

People in the community have been given bottled water to drink. Boiling the water does not remove the nitrate.

Water with high levels of nitrate — a chemical commonly found in fertilizer and liquid waste from septic tanks — can cause a severe illness called blue baby syndrome if ingested by infants.

The nitrate prevents blood from carrying enough oxygen to body cells and tissues.