An Amish mom and her six young kids were killed Sunday when their Pennsylvania home exploded in a fireball so ferocious, emergency workers couldn’t get into the home to save them.

The dad is the only surviving member of the family — because he was away at the time.

The cause of the deadly morning blast remained under investigation, but police said a propane leak inside the two-story home could have been responsible for the tragedy.

Firefighters rushed to the residence in Lamar Township — about 30 miles northeast of State College, home to Penn State University — around 8:30 a.m. and confirmed that seven people were trapped inside when they arrived.

They said the fire was so severe, they couldn’t get into the residence.

“Within a matter of minutes, the house was completely engulfed,” neighbor Christina Duck told the New York Times — adding that the tragic kids “seemed very nice” and would wave at cars driving by.

“There was no saving that house,” she said.

Police said mom Sarah Stolzfus, 34; her four sons ages 11, 10, 5 and 3 and two daughters, 8 and 6, were killed in the blaze.

Duck, who was eating breakfast at the time of the explosion, told WNEP-TV the explosion was so powerful, she could feel it from inside her own home.

“I heard a boom, and I could feel it, and I got up and looked out the window, and I could see the flames through the windows, and I come running outside, and within a minute, the whole house was completely engulfed,” the resident said.

Duck said the family had only lived in the neighborhood for a few months.

She said she regularly saw the chilcren playing in their yard.

Cops said exterior propane tanks located outside the destroyed home did not explode and didn’t contribute to the disaster.

The Pennsylvania State Police and the Fire and Explosion Investigation Unit in Montoursville are investigating.

-Additional reporting by Alex Oliveira and Post wires