JANESVILLE, Wis. -

A Beloit man died has after his snowmobile went into open water on Lake Koshkonong in southeastern Wisconsin.

The Rock County Sheriff's Office said the incident was reported shortly before 1:30 a.m. Saturday. A resident on shore reported hearing someone yelling for help.

As crews responded, a snowmobiler walked into a tavern and said he'd gone into the water and walked to shore, and that his riding partner was missing.

An airboat crew found 47-year-old Willie A. Guzman in the water about 300 to 400 yards offshore. He was pronounced dead at Mercy Hospital.

His riding partner, 46-year-old Lewis Masterson, of Beloit, told authorities they became disoriented on the lake because of darkness and fog, then hit open water.

The Rock County Sheriff's office said it appears alcohol was not a factor.

The Department of Natural Resources said another fatal accident happened Saturday near Mercer in Iron County of northern Wisconsin.

One snowmobiler crested a hill on a public trail and landed on top of an oncoming snowmobiler.

The deaths raise the number of snowmobile fatalities in Wisconsin this season to 18.