Albuquerque police spokesman Simon Drobik told the Journal that an internal affairs investigation has been launched into the handling of the case.
Investigators found Romero, David Zuber and their two other children at a home in northeast Albuquerque on Friday, KRQE reported.
In a criminal complaint obtained by the news station, police said Anastazia was found that same day “deceased and buried in the backyard where David John Zuber stated she would be located.”
"It's tough for detectives to go out to a location, dig a hole and find a dead baby in a bag," Drobik told the Journal. "Then have to build a case around it — just horrible."
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According to KRQE, Romero told investigators "she left Anastazia and her 2-year-old child in the bathtub full of water unsupervised" and that she later found her infant daughter unresponsive. Authorities said neither she nor David Zuber called for police or medical help.
Romero told authorities David Zuber took the body and left their shared apartment after the incident, on Dec. 17, according to the Journal. He told her "it was taken care of" when he returned, the newspaper reported.
Jail records show David Zuber was charged with abandonment or abuse of a child and tampering with evidence while Romero faces one count of child abuse resulting in death.
"It comes down to the two parents who perpetrated this crime and now we have a long investigation to do," Drobik told KOAT.
Authorities continue to investigate.