The state Department of Environmental Quality reports recent test samples of well water used by Oakdale Schools in northeast Oklahoma City contained E. coli.
Department spokeswoman Erin Hatfield said a boil order has been issued for the middle school. The school district has about 625 students enrolled in pre-kindergarten through eighth grade.
The order is for the middle school building water only, Hatfield said.
Water should be boiled for at least one minute. Department officials will report when the water is once again safe for human consumption without boiling, Hatfield said.
The school district does not have summer school and no one is using the water there, Superintendent Kim Lanier said. He said officials from the school and the state will meet Monday to discuss ways to fix the problem.
Recent heavy rains could be to blame, but the district has not had any past issues with the water, Lanier said.
He said the water problem will be corrected before school resumes Aug. 20.