Investigators enlisted the services of a boat mechanic in hopes of pinpointing the source of the odorless, colorless gas that might have flooded the 35-foot boat's cabin while it was anchored to an island on the Illinois side of the river about 50 miles north of St. Louis.
An ex-wife of the boat's owner - Dale Ryan, who was among the dead - said her late husband apparently replaced the 1970s-model boat's central air conditioning. The owner of the marina where Ryan kept the boat wondered whether the built-in generator used Saturday night to run the boat's icebox was to blame, perhaps filling the cabin with carbon monoxide while the couples partied around the campfire.
The Illinois Department of Natural Resources, the case's lead investigator because the deaths happened on a boat, identified the victims as 48-year-old Ryan, his wife, Jody Ryan, her 50-year-old brother, William "Billy" Boehm, and his wife of 28 years, 49-year-old Ruth Boehm.
All of the victims were from Elsberry, a 2,000-resident community near the island.
Jody Ryan's 39th birthday, which was to have been today, inspired the couples' weekend outing that began Saturday, as did the chance to finally get the vessel out on the river for the first time this year after severe flooding that swelled the river in recent months, relatives said.
"This was probably the only trip they were going to take in the boat this year," said Jackie Boehm of Elsberry, the 76-year-old mother of Jody Ryan and Billy Boehm.
Randy Sappington, the owner of the Timberlake Marina in Elsberry, said he partied with the Ryans and Boehms at the boat Saturday night, joining in on some races on the river before leaving. When Sappington's niece returned to the boat with friends the next morning and found it locked, one of them climbed through a window and found the victims unresponsive, Sappington said.
"They were in bed," he said.
Theresa Ryan, Dale Ryan's wife of seven years until their divorce in 2006, said they bought the decades-old boat with two sleeping areas and a small shower-equipped bathroom early this decade.
"It was very nice, but it was old. He maintained everything well," she said of her ex-husband, who headed the maintenance staff for a retirement home for nuns. "We slept on that boat all the time with no problems. I don't know what happened this time."
Dale Ryan was a "jack of all trades" who "took care of everything," having refurbished the boat recently with a new paint job and draperies for outings with Jody Ryan, a former contract painter who became his wife Aug. 2, Jackie Boehm said.
"The houseboat was one of their biggest things. You've got a big houseboat that sleeps four - it's a nice deal. It was an important item in their lives," she said. "It was in good shape, as far as I knew."
The deaths were the latest heartache for Jackie Boehm, a widow with only two of her seven kids still alive. Beyond losing Jody Ryan and Billy Boehm, the mother buried her husband about a quarter-century ago, a daughter who died in her 50s of a heart attack, a son who died of liver disease at age 53, and a son who was 48 when he died of causes the mother declined to discuss today.