Iron County, WI ( - It was another deadly weekend for snowmobilers in Wisconsin. According to the Wisconsin DNR, there were two snowmobile deaths Saturday - one in Iron County, the other in Rock County. The DNR says that the first death occurred near Mercer when a snowmobiler crested a hill and landed on top of an oncoming snowmobiler. The DNR says the two were apparently companions. They say speed appears to be a factor. The other accident happened when a snowmobiler went into open water on Lake KoshKonong in Rock County. The victim's body was found by authorities in water 300 to 400 yards from shore. The DNR reports that these deaths push the number of snowmobile fatalities up to 18 this winter. The DNR says both incidents remain under investigation. Written for the web by Jennifer Austin.