Students and teachers at Maine Elementary School north of Wausau are drinking bottled water after a spike in nitrates was detected in the school’s water supply, school officials confirmed Friday.

The school switched to bottled water about a month ago, immediately after being notified of the test results, said Amy Arlen, communication coordinator for the Wausau School District. This is the first and only test to have revealed a potential issue with the school’s drinking water in the school’s history, Arlen said.

A second test, performed shortly after the first, showed no such spike in nitrates.

But officials with the Department of Natural Resources and the Marathon County Health Department aren’t taking any chances, Arlen said. The school will retest every month for the next two months to be certain there is no danger to students. During that time, students and staff will continue to drink from bottled water.

“We’re being told it could have been an error at the lab, or an anomaly,” Arlen said. “Still, we want to reassure parents that their students are safe.”

The water tests are performed by the Marathon County Health Department and regulated by the DNR.