The city of Portland's water bureau has lifted a 24-hour boil notice after finding clean samples at city reservoirs.

The boil order went out Friday morning after tests discovered the presence of the E. coli bacterium over three days.

Two city reservoirs will be drained and cleaned. The city hasn't yet identified the source of the contamination.

The water bureau advised customers to run all taps for two minutes to purge potentially contaminated water.

The boil order forced the closure of some coffee shops and restaurants. Grocery store aisles were cleared of bottled water downtown.

Officials said 670,000 people were affected by the boil water notice, the largest boil water notice in the city's history.