EPHRATA - Tests showed bacteria in Ephrata's water system for a second time this year.

A test showed non-acute coliform bacteria in a sample taken from city hall, during routine testing done between Nov. 1 and Nov. 4. Samples taken between Sept. 14 and Sept. 20 showed the same type of bacteria in a sample from city hall.

The state Department of Health Web site states the bacteria is not likely to cause illness, but its presence can indicate other disease-causing bacteria.

City Administrator Wes Crago said additional testing showed no other bacteria in the area, nor in the wells operating at the time.

It's unknown how the bacteria entered the water, but city officials suspect a valve closed in April, because of construction, allowed the bacteria to build up, Crago said.

"Despite proactive testing and mandated standards, waterline construction can case this type of disturbance," according to a city statement. "As an additional precaution, the area around City Hall was flushed at length and samples taken since that time have returned clean and free from bacteria."

Residents don't need to boil water and the incident is not related to an April health advisory issued after tests showed non-acute coliform and a single occurrence of Escherichia coli, commonly known as E. coli. An engineering study is ongoing examining the costs and methods of chlorinating the water.

"The city continues with increased monitoring and tests of the water in our lines, at residences, in the reservoirs and directly from our wells," according to a city statement. "Ensuring safe and clean drinking water is the highest priority of the City of Ephrata Water Department."