April 20 (UPI) — A mother and her six children, ranging from 3- to 11-years-old, died in a fire in Clinton County, Pa., when their home exploded.

On Sunday at about 8:42 a.m. EST., emergency response units from nearby Centre and Lycoming counties were alerted to a fire on Long Run Road in Lamar Township. The home of 34-year-old Sarah B. Stolzfus and her children was fully engulfed in flames when first responders arrived on the scene.

State police said the cause of the explosion is under investigation.

Stolzfus and her children, four boys ages 11, 10, 4 and 3, and two daughters, ages 8 and 6, were pronounced dead at the scene.

A propane leak inside the home is a potential cause for the explosion, state police said. There were propane tanks outside of the home that did not explode, nor were they involved in the fire.