BROOKLYN PARK (AP) - Law enforcement and rescue personnel say a seemingly harmless act for charity has potentially dangerous consequences.

Authorities say an online trend that's sweeping across the Midwest has teens and even adults jumping into icy cold lakes, rivers and ponds in the name of charity.

But it has caused serious injuries to a Wisconsin teen and sent first responders in Minnesota searching the dark waters of the Mississippi River for a man who took the challenge and jumped off a bridge in a Twin Cities suburb.

The so-called "cold water challenge" gives participants 24 or 48 hours to record themselves jumping into the water and post the video online. Otherwise, they need to make a $100 donation to a charity.

A Laconia High School junior is recovering from muscle and ligament damage in her knee after jumping into Wisconsin's Lake Winnebago.