FOND DU LAC, Wis. (AP) -- County health officials around Lake Winnebago are urging people to be cautious after blue-green algae blooms were found on the lake.

Officials say hot, humid weather provides ideal conditions for blue-green algae. And Lake Winnebago -- with its high level of nutrients -- is a perfect incubator for blue-green algae blooms.

The algae can produce a harmful toxin when ingested. Signs of illness range from eye, ear and skin irritation, to vomiting and diarrhea.

Jeff Phillips, environmental health supervisor for Winnebago County, says the most serious, and sometimes fatal cases, tend not to be in humans. Phillips says that dogs end up getting sick from it.

Health officials say small children are also more susceptible, since they're more likely to transfer things from their hands to their mouths.