The state Department of Environmental Protection is investigating reports of mine subsidence that has affected at least three homes in Rostraver, Westmoreland County.

The subsidence, which happens when the ground shifts due to the collapse of an underground mine, has heavily damaged two homes and created gaping cracks up to 2 feet wide and 30 feet deep in the ground near a third home's foundation, DEP spokeswoman Helen Humphreys said.

Two families were displaced due to the danger, she said.

The families have mine insurance, which will likely cover costs of the damage, she said.

The Office of Surface Mining also is investigating the incident. Exactly what caused the subsidence and whether it will continue remained unknown.