Three sites tested positive for contamination over the Labor Day weekend, but follow-up testing showed only one positive site remained, city officials told reporters Wednesday. “This is not something that can be solved overnight,” Mayor Brandon Scott (D) said during a news conference Wednesday. “We continue to test locations throughout the city and surrounding county and will continue to do so until the issue is resolved.” A boil water advisory remains in effect for parts of West Baltimore from Riggs Avenue North and South to West Franklin Street and East and West Carey Street to Pulaski Avenue, officials said. The advisory for the south and southwest portion of Route 40, including a precautionary area in Baltimore County, has been lifted. West Baltimore should boil water after E. coli found Gov. Larry Hogan (R) on Wednesday said the Maryland Department of the Environment is working with the Baltimore City Department of Public Works to enforce the federal Safe Drinking Water Act, which sets minimum standards for water quality. The department has a team of engineers on site inspecting the distribution system, treatment systems, pumping facilities and other infrastructure and will inspect some treatment facilities in the affected area, it said in a statement. “Our agencies are working around the clock to assist city officials and help ensure access to clean water,” Hogan said in a statement. “We will continue to provide coordination and technical assistance and make available the resources and personnel needed depending on the situation.” In a series of tweets, Scott thanked residents for their “patience and understanding.” He added that the city will reduce water bills by 25 percent for all residents in the next billing cycle. “I understand this has been an inconvenience for residents,” he said in a tweet. The Baltimore Department of Public Works on Thursday continued to distribute water at three locations — 1401 W. Lafayette Ave., Harlem Park Elementary/Middle School. 3301 Waterview Ave., Middle Branch Park and 500 3rd Ave., Lansdowne Library — with a limit of three gallons per household. Older adults and residents at home could schedule a water delivery by calling 3-1-1.