The California Department of Health is investigating after residents at a house in San Diego reported hearing a thud in the night.
The sound, which sounded like a crunching of a tire, was felt throughout the home, according to the health department.
The agency said the sound came from a cement slab inside the garage.
The contractor who built the garage was notified of the problem by a homeowner, and the slab is now being inspected.
No injuries have been reported.