(CNN) - Drinking water is being shut off at all of Detroit's public schools because elevated levels of lead or copper were found in some of the buildings, the district's superintendent said ahead of the new school year.
The schools will use bottled water and water coolers instead when students return to class Tuesday, Superintendent Nikolai Vitti said.
Recent testing found "higher than acceptable levels ... (of) copper and/or lead" in at least one water source -- such as a fountain or sink -- at 16 of 24 schools, Vitti said in a statement released Wednesday.
And drinking water already had been shut off at 18 other schools because of previously identified water quality issues, Vitti said.
There is no evidence of elevated levels of lead or copper at more than 50 other schools, but test results there are pending, he said.
"Out of an abundance of caution and concern for the safety of our students and employees, I am turning off all drinking water in our schools until a deeper and broader analysis can be conducted to determine the long-term solutions for all schools," Vitti's statement reads.
The Detroit Public Schools Community District, which has more than 100 schools, has not released details of the testing or said what may have caused the elevated levels of copper and lead.
But the city's water department, in a joint statement with the Great Lakes Water Authority, blamed the schools' own aging plumbing systems, and said the schools' lead and copper issues don't extend to the rest of the city.
The drinking water distributed throughout the city surpasses federal and state quality and safety regulations, and the water department has no lead lines connecting to the schools' plumbing, the joint statement reads.
Lead and copper can enter drinking water when plumbing pipes that contain the metals corrode.
Consumption of the metals can lead to a range of health problems, and the Environmental Protection Agency mandates fixes to water systems when lead and copper concentrations exceed certain levels.
Lead consumption can be particularly harmful to children, leading to health effects such as impaired cognition, behavioral disorders, hearing problems and delayed puberty.
The Detroit schools' move comes in the wake of a lengthy water crisis involving dangerous lead levels in Flint, about an hour's drive to the northwest.
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