A department statement says emergency personnel rescued the girls, ages 3 and 4, who were transported to hospitals, where both died.
Deputy Fire Chief Jerald Ziller says a neighbor reported being awakened by a woman screaming. The woman, who was outside when firefighters arrived, was home alone with the girls.
The woman was transported to a hospital, for treatment of smoke inhalation. Ziller says the firefighter was treated and released for a back injury.
Ziller says the home had burglar bars, but firefighters entered through an unsecured sliding glass door.
The cause of the fire is sought. Orange is about 100 miles northeast of Houston.