Vitti ordered drinking water turned off at the 16 schools over the weekend, bringing the total number of schools now using water coolers and bottles to 34. The rest will be shut off "immediately," DPSCD spokeswoman Chrystal Wilson told Crain's on Wednesday morning.

Vitti ordered testing of all schools this spring, after tests in 2016 found elevated levels of the metals. Initial results for 24 schools returned last week found 16 had levels higher than acceptable, he said in the emailed letter. All water sources, including drinking fountains and sinks, were tested. Water is still available for hand washing and toilet flushing.

"Although we have no evidence that there are elevated levels of copper or lead in our other schools (over 50) where we are awaiting test results, 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 said in an emailed statement Wednesday morning.

The detailed results of the testing were not immediately available.

The Associated Press reported in 2016 that elevated copper or lead levels had been found at 19 DPSCD schools. After those results, the district coated some pipes with a silicate to prevent leeching of metal and bacteria, Chalkbeat Detroit reported. The 2016 testing came as a response to the Flint water crisis, in which more than 100,000 residents were exposed to lead-tainted water.

The largest school district in Michigan faces water safety concerns as it deals with deteriorating school buildings that require nearly $530 million in capital improvements.

The city of Detroit also plans to work with charter schools on similar water testing, which it can encourage but not mandate, city spokesman John Roach told Crain's.

"We will be supporting (Vitti) in an advisory capacity through the health department, and the (Detroit Water and Sewerage Department) has offered to partner with the district on any follow-up testing that needs to be done," Roach said in an emailed statement. "We are fully supportive of the approach (Vitti) has taken to test all water sources within DPS schools and to provide bottled water until the district can implement a plan to ensure that all water is safe for use."

The Detroit schools' test results are expected to be posted on the school district website and the city's website. Vitti said letters will be sent home to students when the school year starts next week and parents would be informed via a robo-call system immediately. Teachers reported to work Monday.

The city's water department and regional water board issued a statement Wednesday afternoon to assure their customers that the water they are providing is safe.

"The Great Lakes Water Authority (GLWA) and the Detroit Water and Sewerage Department (DWSD) want to assure Detroit residents and customers of GLWA's regional system that they are not affected by the lead and copper issues that the Detroit Public Schools Community District (DPSCD) is experiencing," they said in a statement. "Aging school infrastructure (i.e. plumbing) is the reason for the precautionary measure of providing bottled water. The treated drinking water provided by GLWA and distributed by DWSD not only meets, but surpasses all federal and state Safe Drinking Water Act regulations for quality and safety. The water at GLWA's treatment plants is tested hourly and DWSD has no lead service lines connected to any DPSCD building."

The organizations said they will assist the Detroit schools district as needed.

The 16 schools in which elevated levels of lead and/or copper were detected in the latest round of testing for 24 schools, according to Vitti's letter:

Academy of the Americas Elementary-Middle School

Adult Education-East

Bates Academy

Bennett Elementary-Middle School

Cass Technical High School

Roberto Clemente Elementary

Clippert Elementary Middle School

Coleman Young Elementary School

Davis Aerospace @ Golightly

Dixon Academy

Foreign Language Immersion

Hutchinson @ Howe

Keidan

Noble Elementary-Middle School

Marcus Garvey

Renaissance High School

Lead is a neurotoxin that can damage child brain development, cause behavioral problems and sicken adults. Copper can cause gastrointestinal distress, and long-term exposure can damage the liver or kidneys.