SAN ANTONIO -

San Antonio police have tracked down and arrested the mother of a newborn boy whose body was discovered at a recycling plant last month.

Nidia Yolibeth Alvarado, 25, was arrested Tuesday night at the Mediterranean Villas Apartments at 1502 Jackson Keller Road.

She has been charged with capital murder.

"It's believed that the suspect gave birth to that baby boy and shortly after, murdered him by strangulation," said San Antonio police Sgt. Javier Salazar.

Investigators said Alvarado checked into a hospital under a fake name on the evening of Dec. 20. According to the arrest affidavit, she was seen on surveillance video arriving at the hospital on that day. She was also seen on video leaving the hospital on Dec. 22, holding the baby as she was wheeled out of the hospital by a staff member.

Police believe she killed the boy shortly after leaving the hospital.

In the arrest affidavit, Alvarado admitted to wrapping a ligature around the baby's neck. She stated she saw the baby crying and then saw it die. She then took the baby to a dumpster near her apartments.

The child's body was found three days later in a duffel bag at a recycling facility.

Alvarado told family members that the baby was sick and had died.

"She gave a fictitious name at the hospital when she did give birth, but detectives were able to find out her true identity and tracked her down just through some really good detective work," said Salazar.

Salazar said several people came forward with information, including a woman who told police Alvarado had asked her if she knew how to perform a self-abortion.

When asked why she killed her son, Alvarado said, "Por amensas" -- "because of threats."

Neighbors at the Mediterranean Villas Apartments, where Alvarado lives, were shocked when they heard about the arrest.

They said she was a quiet woman who often kept to herself but they often saw her around with her children and they remember seeing her when she was pregnant.

Alvarado's 5-year-old boy and 2-year-old girl are now in custody of Child Protective Services. Their futures are uncertain as police investigators try to figure out why a woman who gave a child life would allegedly end it so brutally.

San Antonio police said this case is still an active investigation and they are asking anyone with any information to please contact them.  They said even the smallest details may be significant. The number to call is 207-7635.

On Wednesday afternoon, Immigration and Customs Enforcement officials released a statement in response to Alvarado's arrest:

"U.S. Immigration and Customs Enforcement (ICE) placed a detainer with Bexar County Jail on Nidia Yolibeth Alvarado on Jan. 15.  Ms. Alvarado had been previously removed to Honduras in April 2006."

For a list of recent stories Eileen Gonzales has done, click here.