HOUSTON, Jan. 12 -- A woman and her three young children were killed on Monday in a house fire which occurred in Port Lavaca, a city in the southern U.S. state of Texas, local media reported.

The fire happened around 4:30 a.m. local time (1030 GMT) in a sheet-metal shed behind a Port Lavaca game room, killing the 23-year-old woman, her son and two daughters aged between three months and four years, according to local TV station ABC13.

The father of the children who lives in the one-room shed tried to hack through the front door by using a pickax, but he failed to save his wife and children.

The cause of the fire is under investigation.