Kristepher Benavidez, 25, and Monique Gaxiola, 30, were booked into Pima County jail. They are facing murder charges in the death of their toddler daughter.

An 18-month-old twin girl who was hospitalized earlier this week with severe injuries died Friday morning, said Sgt. Chris Widmer, spokesman for the Tucson Police Department.

Her parents, Kristepher Benavidez, 25, and Monique Gaxiola, 30, are now facing charges of first-degree murder. The pair were arrested Wednesday on suspicion of child abuse but the charges were upgraded after toddler died.

Tucson Fire Department personnel went to a home in the 5200 block of South Newcastle Court, near South Midvale Park Road, about 2:30 p.m. Wednesday.

While Fire Department personnel took one of the toddlers to a hospital, police discovered her twin and a 7-year-old sister at a neighbor’s home. The older child appeared uninjured, but the twin girls had suffered “injuries that appeared nonaccidental,” Widmer said.

Detectives “determined that the father had been physically abusing the twin 18-month old sisters for an unknown period of time. The mother was aware of the abuse but did not report it. Both children suffered severe trauma from the abuse,” Widmer said in a news release.

The oldest child is in the custody of state Child Protective Services.

Bond for Benavidez was set at $20,000 and $5,000 for Gaxiola. Widmer couldn’t say if the bond has been increased.