Carbon monoxide poisoning is suspected of killing a 24-year-old woman on a boat over the weekend on the St. Croix River near Bayport, authorities said Monday.
Two men also on the pleasure craft were hospitalized Sunday after they fell ill, according to the St. Croix County Sheriff's Office.
The three had plans to camp at a beach starting Saturday night, but no one had been able to reach them later, the Sheriff's Office said.
The woman was identified as Ashley G. Speer, of Glenwood City, Wis. Speer was pronounced dead at the scene.
Justin M. Roskos, 25, of Hastings, and Hayden L. Johnson, 27, of River Falls, Wis., are being treated at Hennepin County Medical Center. Roskos, the boat's owner, is in critical condition, while Johnson is in satisfactory condition, a hospital spokeswoman said Monday afternoon.
"Initial investigation indicates this is a probable carbon monoxide poisoning incident," a statement from the Sheriff's Office read. "However, the investigation is ongoing."
Sheriff's Capt. Jeff Klatt said all three were found unconscious in the boat's cabin.
Carbon monoxide can build up from an idling motor, generator or faulty motor exhaust system. The poisonous gas is odorless and invisible.