Drinking water in Detroit public schools tested positive for high levels of copper, lead or both in drinking water for students and faculty.

Detroit Public Schools Community District is awaiting test results from 17 more schools. So far, out of 86 of its 100 public schools, 57 tested positive and the district expects that number to rise after the results come in.

Last month, the school district had to turn off drinking water inside all of its school buildings due to the troubling levels of copper or lead. The testing they performed was not required by any federal, state or city law.

Superintendent Nikolai Vitti said last month, “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,”

A statement from the district said, “This testing, unlike the previous testing in 2-16, evaluated all water sources from sinks to drinking fountains.”

Though the source has not been fully identified, the city water department said aging plumbing systems are to blame, as the issue does not extend to the rest of Detroit. When pipes corrode, lead and copper can enter the plumbing system.

The consumption of metal, especially in children, can lead to a variety of irreversible health problems such as impaired cognition, behavioral disorders, hearing problems or delayed puberty, according to the National Institute of Environmental Health Sciences.

The Environmental Protection Agency mandates water systems to be remedied when lead and copper exceed certain levels.