Germantown, Tennessee, has placed a city employee on administrative leave after a diesel spill contaminated the town's water supply and left some residents without access to clean tap water for over a week.

The city determined the diesel spill "was in part due to human error by a tenured employee," the city confirmed to ABC News.

The employee will remain on administrative leave pending the completion of an investigation, according to the city.

Residents in Germantown, a suburb of Memphis, were told not to use tap water after people reported a strong odor to their tap water on July 20. An investigation into the the cause revealed that diesel fuel was leaking into an underground reservoir from a generator that was powering a water treatment facility due to a power outage.

Residents were told to only use tap water to flush their toilets.

About 100 gallons of diesel contaminated about 4.2 million gallons of water that were being held on site, according to the city.

City officials gradually lifted the restriction on using tap water for residents. Results from a sample collected on Sunday came back all clear, officials said.

"The City continues to execute additional main line flushing to target areas still experiencing residual odor. As required by [the Tennessee Department of Environment and Conservation], the City also continues to sample the water in the main lines at these targeted locations for diesel and its sub-compounds. The City will continue flushing the area until tests are clear," the city said in an announcement Tuesday.

While flushing residential water lines, residents are advised to ensure there is proper ventilation in place in case of strong odors.

Aside from the leak, additional contamination was found deeper in the soil immediately surrounding a pipe that was carrying clean water from the treatment plant into the underground reservoir, Public Works Director Bo Mills said in a recorded message to city residents last week.

"There was a breach in this pipe at this location which allowed the diesel fuel in the soil to enter the reservoir. The pipe has been repaired and the contaminated soil is being removed and contained on site and will be properly disposed of as required by regulations," Mills said.

"Good, clean soil has been acquired to backfill and compact the area in the full repair. The generator has been fully inspected multiple times by outside contractors to ensure that there are no issues with the generator," Mills said.