Carter, 25, was a singer and cast member of the reality show "House of Carters." The married mother of an infant daughter was also the sister of recording stars Nick and Aaron Carter.
Her family confirmed she died Tuesday but released no details regarding the circumstances.
"There were no visible signs of trauma," Richard Mackowiak of the Chautauqua County Coroner's Office told E! News Wednesday. "We are awaiting a toxicology report to determine a cause of death. The body has been released to the family. Results of the toxicology test are made public at the discretion of the family."
TMZ said Leslie Carter had been battling an addiction to prescription medication and was living with family in upstate New York before she died.
The entertainment news Web site cited unnamed sources as saying relatives left her home alone for about an hour Tuesday while they ran errands and came home to find her unresponsive.
Rescue workers were unable to revive her, the report said.