The city of Germantown, Tennessee, has fired an employee who failed to monitor the refueling of a generator at a water treatment facility. As a result, diesel fuel spilled into the city's water supply and left some residents without access to clean water for over a week, City Administrator Jason Huisman said at a town hall on Thursday.

Diesel was able to leak into the water supply through a previously unknown quarter-sized hole in a pipe 6 to 8 feet below ground, according to city officials.

"A general services employee was refueling a generator located adjacent to a ground reservoir. That employee failed to monitor the refueling process as closely as was necessary resulting in the overflow of diesel fuel on the ground, which migrated as far as 15 to 20 feet away," Huisman said.

"That employee, who is a good person, is no longer employed by the city of Germantown," Huisman said.

A city official confirmed to ABC News that the staffer was fired by the city. The staffer had previously been put on leave pending the outcome of an investigation into the crisis.

Residents in Germantown, a suburb of Memphis, were told not to use tap water after people reported it had a strong odor 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. Residents were told to only use tap water to flush their toilets.

Normally the spillage could have been contained by the swift replacement of the contaminated soil with clean soil, but a previously unknown hole allowed diesel to leak into the water supply, according to city officials.

Officials said somewhere around 250 gallons, but not more than 300 gallons, of diesel leaked into the water supply, despite saying earlier in the crisis that about 100 gallons of diesel leaked into the supply.

The city had been using a generator to power the water treatment facility after an intense wind storm had impacted much of Germantown, causing a massive power outage across the city, primarily due to downed trees on power lines, two days before the water crisis, according to city officials.

At the time of the crisis, most of the city's facilities and residences had power restored, but the Southern Avenue water treatment facility -- where the crisis originated -- was still being powered by a generator, according to city officials.

"The technician responsible for refueling the generator failed to monitor the refueling pump while the generator was being refueled, which allowed an overspill of diesel fuel. This diesel fuel then flowed from the generator naturally downgrading it toward the nearby underground reservoirs," Assistant City Administrator Andrew Sanders said at the town hall.

Germantown Mayor Mike Palazzolo apologized to residents for the water crisis and said he plans to launch an independent review into the crisis.

"I do apologize for the health emergency and the health crisis that we have been in for almost two weeks. It has been very disruptive to our everyday lives and I do apologize on behalf of our city team," Palazzolo said.