MADISON, Wis. -- The Madison Water Utility was flooded with calls Wednesday after public health officials issued a new health advisory related to high levels of manganese in some wells.

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A WISC-TV investigation last week detailed some of the utility-management and safety issues with the naturally occurring metal, but new data is prompting new concerns. High levels of the naturally occurring black metal have shown up in two city wells -- even registering above health guidelines in some home taps.

In the past, officials have recommended avoiding high levels of manganese by not drinking dark or discolored water.

But officials now say that new hydrant tests show even clear water can have unsafe levels of manganese in it.

A limited advisory has been issued for the Well Area 3 on the isthmus and Well Area 10 in Nakoma. Officials recommend using bottled water if formula is mixed for infants up to 6 months and for those with liver disease.

The advisory is meant only for the period when the two well areas get flushed, WISC-TV reported.

"The only thing we're concerned about is during flushing, because flushing stirs up the manganese in the distribution system. So you are more apt to get higher levels of manganese for a longer period of time while we're in the flushing operation," said David Denig-Chakroff, manager of Madison Water Utility.

Health officials still say only sensitive groups are at risk -- and only during flushing periods.

Those living in the advisory areas will be getting postcards telling them when the flushing will occur.

A scientific home tap-sampling program to further study manganese will begin soon, WISC-TV reported.

Those who wish to check the number of their well can call the water utility at (608) 266-4665.

The Water Utility Web site also has information on which wells feed into which areas. Go to this Web site and click on the "flushing" map.

Viruses Found In Madison Water

On Tuesday night, WISC-TV also reported on potentially serious viruses that have been found in Madison's aquifer and in two wells.

But Wednesday utility officials said chlorine levels in the wells are keeping everybody safe by killing any viruses.

Utility managers said they double-checked their well chlorine levels on Wednesday, and all but one -- Well 3 -- had levels that met a related Environmental Protection Agency guideline.

"If we meet that standard, we figure we should be able to kill the viruses in question," said Al Larson, principal engineer of Madison Water Utility.

That guideline is set to guard against hepatitis A, but officials said Well 3 was below that unregulated limit until Wednesday, when workers increased its chlorine levels.