The cause of death for Jeffrey Beagley, 34, was not immediately known. Authorities were awaiting the results of toxicology tests and said their investigation was continuing.
Beagley had been facing charges of first-degree murder, reckless manslaughter, attempted sex assault and child abuse resulting in the death.
He had a bottle of chloroform delivered to him a day before he called 911 to report the girl’s death, investigators said. The girl died of chloroform poisoning, according to autopsy results.
Beagley's relationship to the girl has not been released by investigators.
In a shed on the property where the girl was found investigators discovered a tarp made into a privacy tent that had pillows and blankets, a computer, sex toys and a bottle of chloroform, according to KKTV-TV of Colorado Springs.
He was arrested on Dec. 14 and jailed without bond.
Beagley was also facing additional charges for alleged child pornography found on his phone and computer.
He had not entered a plea before his death.
His cause of death is still pending toxicology results.
The investigation into his death is ongoing.
The Associated Press contributed to this report.