Minnesota health officials say most drinking water from municipal systems had safe levels of contaminants in the department's most recent round of testing.
The testing has yielded similar results since health officials first started the monitoring program in 1995, according to the Health Department's Stew Thornley.
"This seems to be about what we find, with approximately 10 municipal systems that have had a positive reading for coliform bacteria," said Thornley. "We sample for chemical type of contaminants -- the things that won't cause immediate illness, but if they're at an elevated level over a long period of time, they could increase a person's risk of having an adverse health effect."
One of the more common contaminants was coliform bacteria. Thornley says it's more likely to show up in smaller water systems, for a variety of reasons.
"Some of the smaller systems don't disinfect their water on a regular basis," he said. "Sometimes when repairs are done or things like that, something can happen. If there's a disinfectant in there, that can provide that additional protection to keep from having a problem."
Thornley says bigger water systems have the resources to disinfect more regularly.
The city water systems that tested positive for coliform bacteria were Avoca, Ceylon, Correll, Johnson, Kasota, Lake City, Lake Elmo, Pine River, Vernon Center, and Wilmont.
Thornley says the problems were quickly resolved and didn't rise to the level of prompting advisories for residents to boil their water.
Other contaminants found in some water systems included nitrates, arsenic and radium. Systems that test positive for contaminants must work to correct the problem.
The Minnesota Department of Health has more information about drinking water testing here.