Six people were pulled alive from the rubble of a Missouri home Saturday morning after an unexplained explosion mangled the residence, authorities said.

All six, said to have been inside the home in Jefferson City when it exploded, were taken to University Hospital in Columbia, Missouri, with moderate to severe injuries, the Jefferson City Fire Department said in a statement.

Some of the six were treated at the location for smoke inhalation, the department said. Two of them were in bad enough shape that they were taken by helicopter for a faster trip to University Hospital trauma center.

Eric Hoy, emergency medical services chief for underlying Cole County, said half the patients required life-saving attention.

"Three of them were in critical condition and required extensive life support procedures," he told NBC affiliate KOMU of Columbia.

Representatives of the hospital did not immediately respond to a request for an update on the patients Saturday nights. Their genders and ages were unavailable.

First responders were called to the home in a neighborhood near the Missouri River to check out a 2:44 a.m. report of an explosion at the residence, according to the city fire department. They soon discovered the home had collapsed, it said.

Footage of the residence in the daylight depicted the structure as twisted, mangled and, in parts, nearly flattened on snow-covered ground.

The Jefferson City Fire Department's Special Operations Rescue Team was enlisted to help pull victims from the rubble, it said.

"Rescue operations were particularly challenging due to the extensive structural collapse and significant debris," the fire department said in its statement.

Jake Holee, Jefferson City Fire Department assistant chief and spokesperson, said the agency was lucky to have the right equipment on hand, along with the help of 37 personnel at the scene.

"We’re real thankful we have that equipment, and we spend the time training," he told KOMU.

Rescuers had to tunnel through multiple layers of debris to pull out at least one of the six, the department said.

In all it took more than three hours to get all six out, as well as to rescue two pets that were turned over to animal control authorities, according to the department.

The cause of the explosion was under investigation.

Jefferson, the state capital, is about 133 miles west of St. Louis.