St. Louis, MO- A St. Louis couple poisoned by a carbon monoxide leak was rescued from their houseboat Sunday morning along the Mississippi River, the Missouri Water Patrol said.

About 9 a.m., water patrol officers were called to help a woman, Mary Reichert, 48, of St. Louis, who was screaming for help aboard a 42-foot-long Sea Ray cruiser near Two Branch Island in St. Charles, the patrol said.

Officers found her husband, Richard Reichert, 59, unconscious on the boat. He apparently passed out because of a carbon monoxide leak aboard the boat, the patrol said.

The Reicherts were flown by helicopter to St. Luke’s Hospital in St. Louis for treatment. Richard Reichert had serious injuries. Mary Reichert had moderate injuries.

The boat’s carbon monoxide detectors were not working, the patrol said.

Carbon monoxide is a toxic, odorless, colorless, tasteless gas produced by the burning of carbon-based fuels, such as gasoline, charcoal and propane.

On boats, the gas is often emitted by engines, gas generators, cooking ranges and heaters, according to the U.S. Coast Guard. The build-up of the gas inside boat cabins, hatches or other enclosed areas is potentially deadly.