Michigan officials say some samples at a Flint high school tested higher than the federal threshold for lead in drinking water.
The Flint Journal reports results posted by the Department of Environmental Quality showed seven of 80 samples from Flint Northwestern High School were above the limit.
More than 97 percent of tests in Flint school buildings this year were below the level.
Flint schools are providing bottled water to students at least through the end of the school year as a precaution.
DEQ spokeswoman Tiffany Brown says the department "will work with the district to address any exceedances."
Flint's water was contaminated with lead in 2014 and 2015, when officials used river water that wasn't properly treated.
Some children were found to have elevated lead levels in their blood.