The blaze, which took place early Wednesday, killed a 13-year-old girl and her brothers, who were 11 and 12, WWL-TV, New Orleans, reported.
Seven others are hospitalized, including the children's father, who is in critical condition after running back into the burning home to help his children.
"He said the only thing he can remember is his little girl saying, 'Papi, ayudame.' And that means in English, 'Papi, help me," neighbor Chantel Guillott said.
The family was in town visiting for Christmas.
A fourth sibling, as well as the family that lives in the trailer, survived.
The fire began in the living room, where the three victims were sleeping, officials said.
Authorities said they are investigating whether candles or space heaters caused the fire.
"I've been doing this for 27 years. and it just seems every holiday, particularly Christmas, we have multiple fatalities," State Fire Marshal Butch Browning.