CONCORD, N.C. (AP) — A third child has died following a weekend house fire in North Carolina, officials said.

Fire-fighting crews were dispatched to a one-story public housing duplex in Concord, northeast of Charlotte, shortly after 1:00 a.m. Sunday.

Firefighters worked to extinguish the blaze and located three siblings inside one of the units. They began life-saving efforts, but two of the children — an 11-year-old girl and a 15-year-old boy — died at the scene, city officials said in a news release. The third child — a 16-year-old girl — was taken to a hospital in critical condition. She died late Sunday.

No other occupants were found inside, and the parents were not home at the time. Officials did not immediately release the identities of the victims.

The occupants of the adjacent unit evacuated before firefighters arrived, according to the news release.

The cause of the fire is under investigation, the city said.