Monahan said firefighters gave CPR to 2-year-old Angelina and Veronica Andreottola before they were taken to Union Hospital in Lynn, where they were pronounced dead.
She said the girl's mother, Crystal Andreottola, was home at the time of the accident.
Monahan said the girls may have somehow opened a remote pool cover, but authorities were still investigating what happened.
She said no foul play was suspected and no charges would be brought.
