WALDOBORO — Heating oil was pumped accidentally into the septic tank at the Medomak Middle School on Wednesday.

The environmental impact is not yet known, but the school has provided bottled water to students and staff as a precaution in the event that the oil contaminated the groundwater.

Regional School Unit 40 Superintendent Steve Nolan said that Maritime Energy delivered oil to the school on Wednesday. When school staff later checked the oil level, they saw that it did not match up with the delivery paperwork. Upon further investigation, the staff learned that the oil had been pumped into a pipe that leads to the septic tank.

The Maine Department of Environmental Protection was called in and Interstate Septic responded and pumped oil out of the septic tank. The amount of oil spilled and recovered was not immediately available.

The administration considered closing the campus, which includes Medomak Valley High School, but determined that if drinking water were provided until the water is tested it would be safe.

“The safety of our students and staff is the top priority,” Nolan said.

A telephone message was left Friday morning seeking comment from Maritime Energy.

A message also was left for the Maine Department of Environmental Protection Friday morning.

Nolan said a meeting was planned later Friday with all parties about how to proceed.