A former Bakersfield woman who pleaded guilty to stabbing her three children to death while living in Scotland has died.

Theresa Riggi, about age 50, was found dead Monday local time in a high-security psychiatric hospital in Nottinghamshire, a county in the East Midlands of England.

Her family in Bakersfield released a statement saying the Rampton Mental Hospital told them Riggi died of natural causes and there was no sign of trauma or suicide.

Some United Kingdom media reports said Riggi's death appeared to be self-afflicted, but did not cite specific, official sources as saying that.

Riggi was found not breathing and an autopsy and toxicology tests are pending, her family's statement said. It described her loved ones as "devastated and shocked by the news."

"When we last spoke on Saturday, there was no indication of any problem," the statement said.

"We are heartened by the fact she kept her faith through this entire ordeal. We very much appreciate your respecting our need for privacy at this time."

A West High graduate, Riggi had pleaded guilty to culpable homicide on the grounds of diminished responsibility in the August 2010 deaths of 8-year-old twin brothers Augustino and Gianluca and their 5-year-old sister Cecilia.

The Daily Mail reported she was ordered jailed for 16 years following her March 2011 plea, and was later transferred from prison to the psychiatric hospital.

The children's bodies were discovered in an Edinburgh townhome after neighbors reported a gas explosion. Riggi was hospitalized after either falling or jumping from a balcony of the house the same day.

She and her estranged husband, oil executive Pasquale Riggi, were going through a divorce and fighting over custody of the children at the time of the killings.

Riggi had disappeared from Aberdeen with the children on July 3, 2010, prompting a missing persons investigation that ended when they were found safe in Edinburgh later that month. She subsequently failed to show up for a hearing in her divorce proceedings.

Pasquale and Theresa, whose maiden name was Butimore, were married by the Rev. Ralph Belluomini in Bakersfield on Sept. 30, 1989, according to a marriage certificate.