Hennepin County epidemiologists are investigating reports that a number of people who were boating around the Big Island on Lake Minnetonka got sick over the July 4th weekend from an undetermined cause.

Carolyn Marinan, a county spokeswoman, said the mother of a sick child alerted the county Monday by e-mail and provided contact information for others who became ill. County epidemiologists are testing those individuals and will send the results to the Minnesota Department of Health for analysis, Marinan said.

At this point, nothing is known about the cause of the illness — whether it was from food or the water.

Marinan said Monday evening that she did not know how many people were sickened. Anyone who was in the Big Island area over the holiday and got sick with vomiting or diarrhea should call the county epidemiology department at 612-543-5230.