Johnston Police said two women who are related died within hours of each other on Thursday.
"I've been here for almost ten years and this is the first time I've had two family members die within those hours apart of each other," said Lt. Lamaz Robinson, of the Johnston Police Department.
Robinson said they received the first call around 4 a.m.
"Officers, along with emergency personnel, responded to the 600 block of Ridge Road in reference to an unresponsive patient," Robinson said.
Trina Simpkins Felder, 36, was rushed to Edgefield County Hospital, where she died some time after.
But what is unusual is that Felder's sister, 48-year-old Willette Simpkins Johnson, also died Thursday at the same house.
"Approximately 3:30 p.m., the sister of this woman was also taken to the hospital with complications of being unresponsive. She arrived at the Edgefield County Hospital where she was later also pronounced dead," Robinson said.
The coroner contacted the Edgefield Police Department for fear that the deaths may have been caused of carbon monoxide.
"We were able to go to the home and find out the source of their heating at the home, and we did rule out at that point in time that carbon monoxide was related to the deaths," said Robinson.
Edgefield Deputy Coroner David Burnett said Felder died of cardiac arrest. An autopsy was also performed on her sister, Johnson, but Burnett said the coroner's office needs more time to rule on her death. He said he doesn't suspect anything suspicious.