-- A California woman was arrested Tuesday for allegedly microwaving her 6-week-old daughter to death, shocking even the most seasoned police detectives who conducted a three-month investigation to determine such a rare cause of death.
"We had never seen a crime this unique and disturbing," Sgt. Norm Leong of the Sacramento County Police Department told ABCNews.com.
Fire officials responded to the residence of Ka Yang, 29, March 17. A relative who had returned home called the department after noticing burns on baby Mirabelle Thao-Lo.
Yang initially told fire authorities she suffered a seizure and had dropped her daughter, who died at the scene, according to officials.
"It was clear the child was burned but the source was mysterious," Sgt. Leong said.
An autopsy conducted by the Sacramento County Coroner found the child had deep tissue burns, although the source of the burns remained unclear.
"The burns were not typical of fire or acid injuries and there was damage to the baby's clothing," he added.
Detectives thought something was peculiar and spent the next three months investigating the case. "Early on, we did speculate it was possible the baby had been put in the microwave," Leong said.
Detectives turned to Google and found three similar cases involving newborns being placed in microwaves in Ohio, Texas and Virginia.
They studied the cases and met with medical professionals, forensic specialists and government agencies.
After the research, it became clear that Mirabelle's injuries were consistent with the kind of burns caused from being placed in a microwave, officials said.
Yang was arrested without incident Tuesday and is being held in Sacramento County Jail. She will be arraigned Thursday.
Yang was alone in the home with Mirabelle at the time of the incident, Sgt. Leong said, although a relative was outside doing yard work.
The baby's father lived with the family but was not home at the time of the incident, police said.
Police said they've been unable to pinpoint a motive and declined to say whether Yang was cooperating.