Investigators say that Keyster showed detectives where the body was.
Keyser was an acquaintance of St. John but their relationship was still being investigated.
WTVR reports family members last heard from the young mother of two at about 7:30 a.m. when she went to her auto to get ready to take her kids to day care.
Deputies searched the property and discovered St. John's cell phone in bushes outside the house and a broken necklace in the yard of the home.
St. John was living with her boyfriend at the time of her disappearance.
Sheriff's officials also said a man was taken into custody in connection the woman's disappearance and was being questioned, according to WRIC.
Authorities say they have recovered the body of a missing Middlesex County mother, not far from her home. Her two children - ages 1 and 3 - were found alone inside.
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John, showed police where her body was located, according to WTVR.
"This is a missing person, under suspicious circumstances", Samson said, adding that it was too early in the investigation to call the case an abduction.
Samson said investigators have interviewed several persons of interest, adding that each cooperated and submitted DNA samples that are being analyzed in a crime lab. "He is obviously a person of interest".
Authorities say Keyser is an acquaintance of St. Johns, but they are not sure how well they knew each other.
- The body of a Virginia mother who reportedly vanished from her front yard has been found and a suspect was taken into custody in connection with her death, authorities announced Thursday afternoon. A K-9 units and air surveillance were joining in the search for St. John.
The poster described St. John as being 5 feet 6 inches tall, weighing 130 pounds and having blue eyes and blonde hair.
She has multiple tattoos including R.J.M. on her right wrist, a princess crown on her left wrist, and a cross on her ring finger.