Pittsburg, PA – Investigators announced Monday that a buildup of natural gas caused a house explosion on Pittsburgh’s North Side Friday.

The explosion happened inside the kitchen of a home on Lovitt Way, but investigators still don’t know what sparked it. It could take a couple weeks to find out exactly what ignited the gas.

No one was home for the explosion, but investigators said the homeowner was supposed to go back to the house later that day.

Five homes in the Spring Garden neighborhood are set to be torn down at 8 a.m. Tuesday morning.