A Florida woman is in jail on a $5 million bond after she plotted to have her young children murder her in-laws, authorities said.

Leticia Silva, 31, of Lakeland, Fla., is accused of mailing her daughters, ages 7 and 9, a knife from jail last December. Silva allegedly instructed the kids to use the blade to murder their paternal grandparents in Greenville, N.C., said Christy Wallace of the Pitt County Sheriff's office.

Silva lost custody of her children after she was arrested in Florida for possession of methamphetamines and sent to prison, NBC affiliate WFLA in Tampa Bay reported. Her young daughters have lived with her in-laws for seven years, Wallace said.

The murder plot went awry after the childrens' grandmother found the knife under one of the girl's pillows in early February, according to Wallace. That's when the grandmother brought both girls to the sheriff's office, where they informed investigators that their mother told them to use the blade to kill their grandparents.

An investigation is underway and police won't speculate on Silva's motives. 

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Silva's friend, Mary Snell, told WFLA that Silva was determined to regain custody of her daughters.

"Her one goal in life was to get them back," Snell told WFLA.

Silva turned herself into the Pitt County Detention Center on Monday, according to sheriff's office press release. She is charged with four counts of first-degree solicitation to commit murder and is being held under a $5 million secured bond.