Dallas police arrested the nanny who police believe was on a phone call while two little girls drowned in a backyard pool.

Marta Sonia Corvi, 58, faces two counts of reckless conduct, both misdemeanors, in the deaths of the 5-year-olds, police said Thursday afternoon.

Investigators believe Sophia Juarez, who lived at the home, and Mia Penoyer of Gwinnett County, the granddaughter of Corvi, wandered outside Sunday afternoon and ended up in the swimming pool.

Sophia was a good swimmer, and her father said he believes his daughter may have died trying to rescue Mia, who could not swim. Eduardo Juarez told Mundo Hispanico he and other family members had gone to the store to buy lunch and left both girls in Corvi's care.

While Corvi was on a 45-minute phone call, the girls went outside, and despite being fully clothed, ended up in the swimming pool, according to Sgt. Bill Gorman with the Dallas Police Department.

Corvi was booked into the Paulding County jail and was awaiting bond to be set Thursday afternoon, according to Cpl. Ashley Henson with the sheriff's office. Corvi was hospitalized in the days following the deaths, police have said.