Coroner Chuck Harris said the initial 911 call went out just after 10 p.m. His office was called in at 11:16 p.m. and identified Michael S. McKinney, 44, of Wanatah and Jennifer Ellenberger, 38, of Crown Point, who were both pronounced dead at the scene, Harris said.
According to witnesses, McKinney's mother had been searching for him and discovered him unresponsive in the cabin of the boat name The Paradox, Harris said in the press release.
Carbon monoxide tests taken at the scene by the Portage Fire Department found gas present in toxic levels, he said.
"There were no indications of any foul play during the ongoing investigation," Harris said in the release.
Toxicology is being performed by the coroner's office to confirm carbon monoxide poisoning, he said.
Portage Police, Portage Fire and the Indiana Department of Natural Resources were investigating. Portage police were not available to discuss the case. An investigator with the Department of Natural Resources said the investigation is ongoing and more information will be released as it becomes available.