"She was having difficulty breathing," Detective Thomas of the Kentucky State Police told Radar. "She became sick five days after she was incarcerated, and then we transmitted her to the hospital...She died about three or four days later."
At the time of her struggle, the jailed 38-year-old's cell mate screamed for help.
"Jail personnel then alerted the hospital, and they said that she was suffering from pneumonia symptoms," Detective Thomas added.
Her medical files and treatment have all been subpoenaed as police conduct a thorough investigation.
"At this time her exact cause of death is still under investigation," the detective added.
Lonnie Brewer, the jail administrator for Perry County jail, previously told Radar that Rachel passed away at Hazard ARH Medical Center Hospital in her native Kentucky.
Rachel reportedly had a long history with drugs, and leaned on her 46-year-old famous sister for help in the past.
According to Star magazine, Rachel has been arrested three times for drug-related crimes.
Meanwhile, Rebecca celebrated her birthday over the weekend with her two young daughters.
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