Residents of Maricopa were urged Wednesday to boil tap water before using it for drinking, cooking, making ice, brushing teeth or washing dishes after two preliminary tests raised concerns about possible E. coli contamination. Global Water Resources, the city’s primary water provider, issued the precautionary advisory. The utility said the initial results are not conclusive and that further testing is needed to determine whether E. coli is present. Under Arizona Department of Environmental Quality requirements, the utility must collect repeat samples at and near the locations where the preliminary samples tested positive. Results are expected about 24 hours after those samples are collected, according to a utility spokesperson. Until the advisory is lifted, residents should bring water to a rolling boil for at least one minute, then let it cool before use. Bottled water is another option for drinking. The possible contamination has not been confirmed. Global Water Resources said it will post updates at gwresources.com/public-notice.