A boil water advisory is still in effect in Brainerd, Minn., after the advisory was issued on Thursday.

Brainerd Public Utilities says the city drinking water is contaminated with coliform bacteria, and officials advise residents to boil tap water before drinking, brushing teeth or cooking to avoid getting sick.

Short-term symptoms such as diarrhea, cramps, nausea, and headaches can be caused by drinking contaminated water.

Officials say the city’s drinking water could have been contaminated with coliform bacteria due to construction on July 27, although the root cause is still unknown.

The city is chlorinating the water system and will flush the chlorinated water and collect samples to confirm there are no total coliform bacteria remaining in the system.

The issue is expected to be resolved by Monday.