An E. coli bacteria contamination detected last week in the water system RAF Alconbury had been eliminated by Monday afternoon, but base officials said Tuesday that it was still unclear how the bacteria entered the system in the first place.

Alconbury residents were told to boil their water or stick to the bottled variety on Oct. 4, after routine tests detected E. coli bacteria in the base’s system.

The system was declared safe at about 12:30 p.m. Monday, after a three-day cycle of tests showed no more bacteria, Master Sgt. Richard Romero, an Alconbury spokesman, said Tuesday.

The contamination was within the base’s own water system, and was not from off-base origins, he said, and it did not appear to have been malicious in nature.

With the bacteria now gone, Romero said finding a definitive source is not easy.

Bioenvironmental engineers had “a couple educated guesses” regarding what caused the contamination, Romero said, but nothing concrete. Romero would not say Tuesday what those possible sources were.

“We’re not going to speculate on anything we don’t know for a fact,” he said.

The base tests the water system on a monthly basis, and more chlorine was put into the water after the E. coli was detected last week, Romero said.

The Alconbury community was warned about the bacteria on the night of Oct. 4, according to a release sent out by the base on Friday. A hot line was set up and an information booth was available at the local community center. Flyers also were distributed and a base-wide e-mail was sent out.

E. coli bacteria can cause diarrhea, cramps, nausea and kidney failure in some cases, according to the U.S. Environmental Protection Agency’s Web site. A form of bacteria that originates in the intestines of humans and animals, E. coli in a water system indicates that the water is contaminated with human or animal waste, the Web site states.

During rainfalls or other types of precipitation, the bacteria may be washed into creeks, rivers, streams, lakes or groundwater, according to the EPA. When these waters are used as sources of drinking water and not treated or inadequately treated, E. coli may end up in drinking water.

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