ST. PAUL, Minn. (AP) -

The state Department of Health is warning Minnesotans to be wary of scam artists selling water treatment systems.

Officials have seen a rise in complaints about deceptive sales pitches for water treatment systems, following investigations of groundwater contamination in Washington County and elsewhere in Minnesota.

The Health Department says in most cases, the systems are unnecessary and are being sold for thousands of dollars more than they were cost if purchased through a reputable water treatment company.

Officials say even legitimate water treatment systems can be expensive. If those systems are poorly operated or maintained, they may have limited effectiveness and could make the water quality worse.