Updated

Baltimore fire officials say the cause of a January blaze that killed six children remains undetermined.

The Baltimore City Fire Department said Thursday the cause of the Jan. 12 fire is unknown "after months of an intensive comprehensive investigation."

Fire Chief Niles Ford says the department's heartfelt condolences continue to go out to the family.

The Jan. 12 fire killed six of Katie Malone's nine children, including 11-year-old Bridgette; 10-year-old Amelia; 3-year-old twins Amanda and Zoe; 2-year-old Billy; and 8-month-old Daniel.

Malone's 8-year-old daughter Erin managed to get her mother and siblings Jack and Jane, aged 4 and 5, out of the house, which collapsed before her other six siblings could be rescued.