Frederick County authorities are releasing the names of the two girls killed in a house fire in Myersville.

Sheriff's Cpl. Jennifer Bailey said Friday that 3-year-old Madigan Lillard and her 6-year-old sister Sophie were trapped inside the burning house when firefighters arrived late Thursday night. Police say the intense fire and structural instability prevented firefighters from reaching the girls.

Bbailey says the girls' 8-year-old sister Morgan is being treated at Children's National Medical Center in Washington. The girls' father, 39-year-old Jack Lillard, is at MedStar Washington Hospital Center. Bailey said the girls' mother, 33 year old Angela Lillard, has been released from Frederick Memorial Hospital along with 7-month-old Sadie Lillard.

Bailey says a Middletown Volunteer Fire Company firefighter who suffered injuries remains at Frederick Memorial.

The investigation is ongoing as fire investigators work to determine the cause of the blaze. The loss of the home and its contents is estimated at $200,000.