Tinessa Hogan, 36, was arrested Tuesday night on two counts of first-degree murder, news outlets reported.
The bodies of Destiny Hogan, 9, and Daysha Hogan, 7, were found June 22 floating in a canal in Lauderhill, which is near Fort Lauderdale.
Residents in the area had told investigators that Hogan had offered to baptize people in the canal a day before the girls’ bodies were found, police said last month.
Destiny’s body was spotted first on the afternoon of June 22. Hours later, authorities found her sister’s body nearby.
Authorities said last month that the family lived near the canal, and that there were no records of of child welfare workers responding to the home.
It was not immediately known whether Hogan has retained a lawyer who can speak on her behalf.