Hannah Anderson Update: Cause of death for brother of rescued Calif. teen unknown due to "extensive charring", M.E. report says

(CBS) SAN DIEGO - The cause of death for Ethan Anderson, the 8-year-old brother of Hannah Anderson, the California teen who was kidnapped by a family friend and later rescued in the Idaho wilderness, could not be determined due to the "extensive charring" of his entire body, newly released medical examiner's reports obtained by CBS News' Crimesider reveal.

PICTURES: Calif. teen rescued in Idaho wilderness

Christina Anderson, the mother of Hannah Anderson, was determined to have died of blunt force injury to the head, the San Diego medical examiner's office determined.

The report says authorities responded to a home in Lakeside, later identified as that of James Lee DiMaggio, a longtime friend of the Anderson family, on reports of a fire, Aug. 4. After distinguishing the flames, a firefighter observed human feet "protruding from underneath a tarp" in the garage. It was later determined to be 44-year-old Christina Anderson.

The report says she was found face down and was wearing a red Disney tank top, faded black denim jeans and had a ring on her finger that read, "LOVE." Her ankles were bound together with a zip tie and duct tape was wrapped around her neck and mouth. The large roll of duct tape was still attached to her head. She was found to have a wound to her neck, skin abrasions, burns, and skull fractures, according to the report. It was previously reported that a search warrant revealed a crowbar was found next to her head.

The Anderson family dog was also found dead from a gunshot wound in the garage, which was detached from the burned out log cabin residence.

The remains of Ethan Anderson were not found until the next day "amongst rubble," the report says. His remains were "burned beyond recognition," the medical examiner noted. DNA testing confirmed the remains were those of Ethan on Aug. 9.

According to the report, he had fractures of the skull and ribs, among other bones. The report says these "were most likely thermal-related, but, traumatic causes cannot be completely excluded." No cause of death could be definitively determined.

"It is unknown whether [he] was alive at the time of the fire or already dead," the report reads.

James Lee DiMaggio, 40, is accused of murdering Christina Anderson and her son Ethan, setting his home on fire, and kidnapping 16-year-old Hannah on Aug. 4. He was killed six days later in an FBI shootout in the Idaho wilderness. Hannah Anderson was rescued and returned to California.

The San Diego County sheriff's department has said DiMaggio was close to the Anderson family, including both children. The medical examiner's report, citing information from a sheriff's detective, says that on Aug. 3, the day prior to the murder and abduction, DiMaggio had been asked by Christina Anderson to pick up Hannah from cheerleading camp.

August 3 was the last day Christina and Ethan Anderson were seen alive.

Complete coverage of Hannah and Ethan Anderson on Crimesider