Dayle Haddon, a model and actress who graced many a magazine cover in the 1970s and 1980s and bucked the fashion industry by continuing to model later in life, was found dead at her daughter’s home in Bucks County, Pa., on Friday morning. She was 76.

The cause of her death was believed to be carbon monoxide poisoning, the authorities said. Emergency personnel discovered Ms. Haddon’s body at around 6:30 a.m. in a bedroom on the second floor of the house, and also found a man passed out on the first floor of the home, according a statement from the Solebury Township Police Department.

High levels of carbon monoxide were detected at the property, and three emergency responders were treated for carbon monoxide exposure. A faulty flue and exhaust pipe on a gas heating system is believed to have caused the carbon monoxide leak, the authorities said.

Walter Blucas, 76, the man who had passed out, was transported to Robert Wood Johnson University Hospital and was in critical condition on Saturday, according to local authorities and Ms. Haddon’s daughter, Ryan Haddon. Mr. Blucas is Ryan Haddon’s father-in-law.

Ms. Haddon’s life is a winding tale of reinvention and creativity, as her daughter recalled in a phone interview on Saturday evening. Her adventure began in Montreal, where she started to train at age 5 in rigorous dance rehearsals.

As a teen, she went on to perform for some of the most esteemed troupes in Canada, including for Les Grands Ballet Canadiens. Ms. Haddon took on modeling to pay for her classes. She found success in the side gig and was named “Miss Montreal” in her late teens.