A third person has been arrested in connection with the murders of a pregnant Texas teenager and her boyfriend, police say

(CNN) — A woman has been arrested in connection with the slayings of a pregnant Texas teenager and her boyfriend after their bodies were found in a car in San Antonio last month, authorities said. This is the third arrest in the case.

Myrta Romanos, 47, was arrested on charges of abuse, alteration, destruction or concealment of a corpse and tampering with evidence, according to San Antonio Police Lt. Michelle Ramos at a press conference this Wednesday.

Ramos said police believe she is the stepmother of a 19-year-old suspect arrested earlier this month.

The bodies of Savannah Soto, 18, who was nine months pregnant, and Matthew Guerrera, 22, were found in a car parked near a San Antonio apartment complex on Dec. 26, each with gunshot wounds.

Savannah Soto and Matthew Guerra. (Credit: Family Handout/KSAT)

According to Leon Valley, Texas, police, Soto, who had passed her pregnancy, was reported missing by her family when she missed an essential medical appointment.

On Jan. 4, Christopher Preciado was arrested on suspicion of capital murder in her death, as well as altering, destroying or concealing a corpse and abuse of a corpse, Bexar County court records show.

The 19-year-old’s father, Ramon Preciado, 53, was arrested on charges of abuse of a corpse, the San Antonio Police Department said in a statement, allegedly helping his son “move the body.”

The father and son were arrested after San Antonio police shared a surveillance video showing a dark-colored truck and the victims’ vehicle approaching each other in the area where they were found.

Police later found the truck and eventually the suspects’ home, authorities reported at the time.

In this photo you can see Savannah Soto in a photo shared by authorities. (Credit: Texas Department of Public Safety)

The lieutenant said Wednesday that surveillance video also contributed to Romanos’ arrest, after information circulated on social media about the possible involvement of a third person.

The department’s forensics unit was able to “develop information” from the video that showed Romanos was “involved” on the night of the murder, according to Ramos. Romanos was seen in a dark-colored van returning home that night with two suspects in the van, Ramos said.

Romanos is currently being held on US$1.1 million bail, according to magistrate records.

Monica Guerrero, Christopher Preciado’s attorney, told CNN on Wednesday that she had no comment at this time. Ramon Preciado’s attorney, John Kuntz, told CNN on Wednesday that he will no longer represent him. It is unclear whether he retained separate legal representation.

CNN could not determine whether the Romanos have an attorney.

— CNN’s Melissa Alonso and Nouran Salah contributed to this report.