DETROIT — Drinking water is being shut off at all Detroit public schools because the water in 16 of them was found to have high levels of lead or copper. Officials believe old fixtures, not the water source, may be to blame.

Superintendent Nikolai Vitti said Wednesday that he's turning off water at all schools "out of an abundance of caution" while more tests are performed.

Detroit Public Schools Community District has more than 100 buildings and serves more than 40,000 students. The new school year starts next week.

Get Breaking News Delivered to Your Inbox

The district operates independently from City Hall, but Vitti says he's working with Mayor Mike Duggan on water-quality issues.

The agency providing water, Great Lakes Water Authority, says its water surpasses all federal standards.

In nearby Flint, tap water became contaminated with lead in 2014 after officials switched from the Detroit system to the Flint River to save money. The City of Flint didn't implement proper water treatment procedures to stop the corrosive water from breaking down aging lead pipes, exposing many residents to the potent neurotoxin in their drinking water. Some children were found to have elevated lead levels in their blood, leading to long-term health concerns. The EPA says there is no safe level of lead.