The mayor of Flint, Michigan, has declared a state of emergency over lead in the city’s drinking water. Last year, the city switched its water source from the Detroit system to the Flint River. Despite switching back in October, Mayor Karen Weaver said lead levels remain higher than the federal threshold in many homes. A study released in September found the proportion of children under five with elevated lead levels in their blood nearly doubled following the switch. Weaver, who just became Flint’s first woman mayor, made the announcement Monday night.