ST. CHARLES COUNTY, Mo. — Two children died Friday morning after a St. Charles County home caught fire.

Crews responded to the home around 7:45 a.m. located in the 2900 block of Highway 94 South in Defiance after a report of an explosion, according to St. Charles County police.

Authorities said fire happened in the Augusta Fire District and the Cottleville Fire Department took the lead in the response. Upon arrival, the house was engulfed in flames. When crews went inside, they said they didn't find anyone initially due to the fact that only a small portion of the scene had a "searchable space."

Once crews could search more of the area, firefighters discovered the two victims, a four-year-old and six-year-old.

They were pronounced dead at the scene.

Authorities said five people were inside the home at the time. Three adults escaped. One of the adults and a police officer on scene were treated for non-life-threatening injuries.

It's unclear what started the fire. The state fire marshal's office is now investigating.