TOWN OF PORTLAND, Wis. -

Officials have identified the man who was found dead and the man injured inside a rural Dodge County cabin Monday night.

The Dodge County Sheriff's Office said 46-year-old James S. Greevers Jr. was found dead inside the cabin on River Oaks Road in the town of Portland, Wisconsin. His father, James S. Greevers Sr., 69, remained hospitalized Wednesday.

The sheriff's office said it received a call Monday from concerned family members asking deputies to check on the welfare of two men who were staying at the cabin.

A family member reported that the men were overdue to return home to Milwaukee from a weekend deer hunting trip and the family was unable to reach either man by phone, officials said.

No one responded when deputies knocked at the cabin door, but they saw through a window that one of the men on the floor was unresponsive, according to the report.

Deputies requested EMS and forced entry into the cabin and found James Jr. dead and James Sr. with a potential life-threatening medical problem.

Officials said James Sr. was taken to a nearby hospital and later transferred to an intensive care unit in Madison.

The Dodge County medical examiner is investigating the death along with the sheriff’s office.

A cause has not been determined, but carbon monoxide and other environmental causes were being investigated, according to the report.

"There was a furnace in the residence that may have been malfunctioning," Sheriff Dale Schmidt said.

He's warning others, as the weather gets colder, to check the furnace to make sure it's working properly. 

"It is life threatening," he said. "Carbon monoxide is a tasteless, odorless gas and you might not even know what the effects are if you succumb to it." 

Both men are from Milwaukee, the sheriff's office said.