A Philadelphia woman admitted suffocating her 7-month-old son and 3-year-old daughter with a bedsheet during a visit to Florida, authorities said Thursday.

Sophia Hines, 40, took a bed sheet and held it over the mouth of her son, St. Leo, according to a police report. She then used the same bed sheet to cover the mouth of her daughter, Ariel.

Hines was being held without bail at the Broward County Jail. She has been charged with two counts of premeditated murder, which could potentially carry the death penalty. No attorney was listed to represent her.

Police say Hines gave them no explanation for her actions.

The homicides occurred during a visit to a relative's home in Miramar, located a few miles north of Miami. Police said Hines arrived a week ago with her two children. They also said Hines stayed by herself with the kids until she called the relative, Neisha Nettleford, on Wednesday afternoon and told her to "come home now."

The report said that Nettleford saw Hines crying as the two children lay side-by-side and in a face-up position on a bed in a master bedroom.

A neighbor told WTVJ-TV (http://bit.ly/1U7X0xb ) that a frantic woman went to his home to use his phone and made several calls. "She just seemed a bit hysterical," he said.

Two police officers responded to the 911 call and were directed to an apartment behind the Miramar home, said police spokeswoman Tania Rues. Rues said that police performed CPR on both of the victims until fire rescue arrived and pronounced the children dead.

Rues added that the person who called 911 has not been identified.