SACRAMENTO (CBS13) – Twin Rivers Unified School District is set to investigate concerns with drinking water at Grant Union High School on Friday.

Some water fountains and faucets are continuing to show elevated levels of lead and copper, the district confirms. However, Twin Rivers officials say they believe they are closer to narrowing down the source of the problem.

A routine test done over the summer revealed elevated levels of lead and copper, prompting more rigorous testing to try and find where the contamination was coming from.

Officials tested the water supply of the school and it came back clear. The school’s swimming pool and stadium also have tested negative.

The school is providing students and staff with bottled drinking water until the issue is fixed. People can still use faucets to wash their hands, officials say, as lead and copper does not permeate skin.

Officials are working with Sacramento County’s environmental management department in the investigation.

The investigation will continue into the weekend.