Firefighters quickly extinguished a fire that broke out in a modest, cinder-block bungalow in North Charleston on Tuesday morning, but its two occupants were killed by the dense smoke that filled their home.

Roy House, 79, and his wife, Betty, 76, of 7238 Mazyck Road, were pronounced dead at the scene, Chief Deputy Coroner Judy Koelpin said. Autopsies showed both died from smoke inhalation.

The North Charleston Fire Department was dispatched to the fire at 8:24 a.m., said Bianca Sancic, public information officer for the Fire Department. A passerby called 911 and reported seeing smoke and hearing something that sounded like an explosion.

Mazyck Road is off Ashley Phosphate Road, not far from Interstate 26.

When the first engine arrived the crew reported seeing fog and smoke, Sancic said. Firefighters entered the home and began knocking down the fire and searching for occupants. They quickly pulled out one person. A few minutes later, they came out with another.

Chaplains from the Coastal Crisis Chaplaincy were at the scene, praying with firefighters after the bodies were removed from the property.

The fire was declared under control within 25 minutes, Sancic said.

The cause of the fire has not been determined, Sancic said. Investigators will try to determine if smoke detectors were installed and working, she said.

"The smoke is a significant threat in a fire," she said. Most fire fatalities caused by smoke inhalation are in situations in which smoke detectors are either not installed or not working, she said.

Damage to the house was kept to a minimum, Sancic said.

There was heavy smoke damage throughout and fire damage in several rooms, but the roof was not damaged and the house could be salvaged, she said.

A next-door neighbor, who did not want to be identified, said the Houses were in poor health. She said the couple had lived in the house for years and were active, concerned neighbors until their health deteriorated. At least one of them used an oxygen machine, she said.

A charred oxygen tank could be seen in the yard as firefighters cleaned up around the house.

Reach Andy Paras at aparas@postandcourier.com or 937-5589. Reach David W. MacDougall at 937-5655 or macdougd@postandcourier.com.