Two women and their pet dog were found dead of carbon monoxide poisoning in their Lindstrom home Monday.

The women, Lisa Marie Kantorowicz, 53, and Cheryl Carmel Adams, 56, are part of a surge in carbon monoxide deaths in recent years.

Twenty-two people died of accidental carbon monoxide poisoning in Minnesota last year, according to a preliminary calculation by the Department of Health. That’s the highest number since at least the 1990s. Health and law enforcement officials stress that such cases are usually preventable with carbon monoxide detectors, which were not found in the Lindstrom house. Kantorowicz’ and Adams’ furnace was clogged and covered with ice outside, contributing to the buildup of the odorless, colorless gas.

“My guess would be the furnace was probably out of repair or hadn’t been checked in some time,” said Lakes Area Police Chief Kevin Stenson.

“Minnesota has had its share of deaths due to faulty furnaces or clogged chimneys, and it’s frustrating from a law enforcement point of view,” said Stenson. “It’s tragic and it’s something that we work hard against.”

He said investigators couldn’t enter the home for “quite some time” because the carbon monoxide levels were so high. A patrolman was treated and released from the hospital after experiencing headaches and dizziness being inside the house.

Carbon monoxide deaths in Minnesota have been climbing since hitting a low of seven in 2010. “They’re preventable deaths,” said Jon Cole, medical director of Minnesota Poison Control System.

The state’s hospitals reported 514 cases of carbon monoxide poisoning last year to the Minnesota Poison Control System, up nearly 30 percent from the year before.

Such cases happen more in winter, when people are turning on furnaces and heaters. While healthy people often have very low concentrations of carbon monoxide in their body — from, say, breathing in smog or smoking cigarettes — those reacting to more dangerous levels of the gas can become dizzy, vomit and get headaches. The similarity to other, more harmless ailments can mask the danger of what’s really going on.

“The initial symptoms are often quite vague, so people chalk it up to eating something poor, or the flu, or not sleeping well the night before, but in fact they may be suffering from carbon monoxide poisoning,” said Cole.

When victims arrive at the hospital, doctors give them oxygen masks and in more severe cases, treat them in what’s called a hyperbaric oxygen chamber that floods their lungs with oxygen.

Xcel Energy said it receives several hundred calls a year from people whose carbon monoxide detectors go off. Often the problem is that fuel-burning appliances are not venting properly or malfunctioning in some way, according to Tom Anderson, manager of gas emergency response.

“This type of incident [in Lindstrom] is not a common occurrence by any stretch of the imagination, but the potential is there if your equipment isn’t maintained,” said Anderson.

In December, carbon monoxide killed Michael Mechley, 39, and his daughter, Charlene, 11, in their trailer in Rice Lake Township.

Larry Cozzi checked on his son, Mechley, and grandkids in their trailer down the road.

“Mikey was gone. He was sitting on the couch and he was gone; he had been gone for quite a while,” said Cozzi. "So I turn around and went to the bedroom and I found the 11-year-old — she was laying on the floor between the bunk beds. So at that point in the game I heard the 15-year-old girl, she hollered, ‘Grandpa!’ ”

He called 911 to report his son and granddaughter, Charlene, were dead, and took his other granddaughter, Karley, outside.

Police discovered unusually high amounts of carbon monoxide in their systems.

“That’s one of the worst killers,” said Cozzi. “It just puts you to sleep and you don’t know you’re going to sleep.”