PORTER, Ind. (AP) -- Rip currents have been blamed for the drownings of two teenage swimmers in Indiana waters this summer, and now they're the subject of warnings being issued by the National Weather Service.

The warnings are being issued by the weather service's Chicago region, which includes the Lake Michigan shoreline from Kenosha, Wisconsin, to New Buffalo, Michigan.

The warnings are sent out via weather radio, to emergency agencies and local media, and through the weather service's Web site.

Meteorologist Bill Wilson says the warnings are an extension of those that have been in place on the country's east and west coasts for several years.