The coroner's office says a Los Angeles mail carrier found dead inside her postal truck amid scorching temperatures died primarily from overheating, the AP reports. Temperatures reached 117 degrees during the week in July that Peggy Frank died in the Woodland Hills neighborhood. The Orange County Register reports that the 63-year-old died of hyperthermia, or abnormally high body temperature. Investigators say she had pre-existing health conditions including obesity and heart disease. Frank had worked for the United States Postal Service for 28 years. The USPS said in July that its employees undergo required training about working during extreme weather. The federal Occupational Safety and Health Administration is investigating the death. (More US Postal Service stories.)