A mystery is unfolding in Port Huron, where police have discovered a 90-year-old woman and her 65-year-old son dead in their home.
They were discovered after neighbors called police after not seeing the pair for a while, and noticing mail piling up on the porch.
Police initially suspected carbon monoxide poisoning, but say there was no trace of the gas in their home.
There were no outward signs of trauma on the bodies.
The mother and son may have been dead since Christmas.