INDEPENDECE, Mo. (AP) — Police say a natural gas leak sparked an explosion that leveled an Independence home.

Authorities announced the cause of the blast Tuesday night. They haven't determined the source of the leak.

Firefighters were called to the single-story home Tuesday afternoon. All of the walls caved in and only the fireplace was left standing. The three people who occupied the home were away during the explosion. No family members or neighbors were injured.

The family had lived in the house since 1971.

Several pets were in the home at the time. A pug and a border collie were thrown into a neighbor's yard. They are being treated at the Great Plains SPCA animal shelter. Three other pets are presumed dead.