The 17-year-old girl who broke out of her Perris, California, home Sunday had been working on an escape plan with one of her 12 siblings for more than two years, prosecutors said.

Riverside County District Attorney Mike Hestrin revealed during Thursday’s press conference that the teen girl who fled from her filthy home and called police had been devising an escape plan with her sister for years. He said the pair had escaped through a window together, but the other sibling went back into the home, according to The Telegraph.

“The 17-year-old had been working on a plan with her sibling to escape the abuse for more than two years,” Hestrin said.

“She took her sibling with her through [a] window, but that sibling became frightened and went back.”

ORIGINAL Story: House of Horrors! Parents arrested after 13 emaciated siblings, some shackled, rescued from decrepit ‘foul-smelling’ home: Cops

As CrimeOnline previously reported, Riverside County police arrested David, 57, and Louise, 49, Turpin after their 17-year-old daughter escaped their Perris home and called for help. The teen allegedly told officers that she and her 12 siblings were being starved and held captive in the filthy home–and presented pictures that corroborated her story.

Reports indicated that investigators found three of the children chained to furniture in the “foul-smelling” home.

“Deputies located what they believed to be 12 children inside the house, but were shocked to discover that 7 of them were actually adults, ranging in age from 18 to 29,” police said in a statement. “The victims appeared to be malnourished and very dirty.”

The couple is facing multiple charges, including torture and false imprisonment. They pleaded not guilty to all charges during a Thursday court appearance.

They both remain jailed on $9 million bail.

[Featured Image: David and Louise Turpin/Riverside County Sheriff’s Department]