Authorities said a puppy taking a walk on a Massachusetts beach with its owner uncovered a human bone, which led to the discovery of several other bones.

Bill Barrett of Newbury was walking his chocolate Labrador retriever Saturday morning on Plum Island Beach when the puppy made an unusual discovery. Barrett said it appeared to be a human leg bone, and it was still covered with a sock.

Investigators with cadaver dogs later found several more bones. Police on Sunday confirmed the bones are human.

A coordinated search took place covering a 3-mile area on the beach following the findings, and continued into the federal refuge portion of the island, Fox affiliate WFXT reported.

Essex district attorney spokeswoman Carrie Kimball Monahan told the Boston Globe that police are investigating and will be looking at missing persons' cases to try to identify the remains.

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The Associated Press contributed to this report.