WICHITA, Kan. -- Authorities say Yesenia Sesmas, the woman accused of killing Wichita mother Laura Abarca-Nogueda and kidnapping her six-day-old baby is in the U.S. Illegally.

Laura Abarca-Nogueda and her newborn infant, Sophia KWCH

Wichita police said Sesmas faked being pregnant for months and had been a longtime acquaintance of the 27-year-old mother, who was found dead Thursday at her home. Authorities launched a massive search for the new mother’s six-day-old infant Sophia, who was found safe in Dallas days later.

In an interview with KUVN-TV of Dallas-Fort Worth, Sesmas, 34, said that Abarca-Nogueda had agreed to turn over her newborn daughter to her but reneged on the agreement. She admitted killing the woman, but said it was an accident.

Immigrations and Customs Enforcement officials confirm to CBS affiliate KWCH that Sesmas is an undocumented immigrant. They say her name was first flagged to them in July, when she was arrested in another kidnapping case.

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Sesmas had been arrested — but was never charged — on suspicion of threatening a pregnant woman with a knife and trying to hold that woman’s two daughters for ransom. She posted bond and was released less than 24 hours after her arrest, said Col. Brenda Dietzman, undersheriff for the Sedgwick County sheriff’s office in Wichita, Kansas.

The family in that case was able to escape unharmed. The victim told KWCH that Sesmas seemed “fascinated” with her pregnancy.

U.S. Immigration and Customs Enforcement did not receive the July 25 list of arrests from the Sedgwick County sheriff’s office that included Yesenia Sesmas’ name until the following day, and by that time she had been released, ICE spokesman Carl Rusnok said Wednesday. The agency would have asked that Sesmas, a Mexican national, be detained if she had still been in jail, Rusnok said.

Sesmas reportedly then missed a court date and a warrant was issued for her arrest, but authorities weren’t able to locate her until her arrest in the latest case in Dallas.

Sesmas was jailed in Dallas on a Kansas warrant, with first-degree murder and kidnapping charges pending, and Kansas authorities are seeking her extradition. The station reports ICE now has a detainer on her, and should she be convicted she’ll serve out her sentence in Kansas before beginning immigration proceedings.