Shane Del Rosario died naturally

UFC heavyweight Shane Del Rosario died of natural causes earlier this month, according to his death certificate, a copy of which was obtained by MMAJunkie.com.

The Orange County (Calif.) coroner's office ruled that Del Rosario, 30, suffered from brain damage due to a lack of oxygen and an abnormal heart rhythm, the website said. The official cause of death was listed as anoxic encephalopathy, ventricular fibrillation and Long QT syndrome.

Medical examiners also found traces of several illegal substances in Del Rosario's body, including cocaine, opiates and THC, an active ingredient in marijuana. The drugs were found during a urine screen but were not listed as direct causes of death.

Additionally, the certificate recorded Del Rosario's official date of death as Dec. 3, which reflects the date a physician pronounced him brain dead in Newport Beach, Calif. The UFC had announced his death on Dec. 9.

Del Rosario was hospitalized Nov. 26 after his roommate, UFC fighter Ian McCall, found him unconscious. He was admitted to the coronary unit, where it was determined he had suffered sudden cardiac arrest.

Following his death, Del Rosario's family stated interest in starting a charitable foundation to aid research on Long QT syndrome.

The heavyweight had been scheduled to fight at UFC 168 on Dec. 28, but withdrew due to a rib injury. He began competing professionally in mixed martial arts in 2006, following a successful stint in Muay Thai.