Newtown Township police say Peco crews were digging a trench shortly after 11:00 a.m. Monday in the vicinity of Penns Park Road and Route 232 in Wrightstown Township.
Police say workers were digging in preparation for a new home to be built.
There they discovered the vault, and when they lifted the lid they discovered a casket.
The casket was opened by police, who saw baby bedding inside. However, the remains were soon identified as those of a dog.
Investigators say the current property owner had no knowledge of the grave, nor did the previous owner.