Another child burned at a day care center in Mexico is being treated at Shriners Hospital in Sacramento, the fourth child brought here for care.
The U.S. Embassy confirmed that the 3-year-old boy was in critical condition, with third-degree burns on 70 percent of his body.
A Friday blaze at the ABC day care center in Hermosillo left at least 44 people dead, with dozens hospitalized.
The conditions of the three other children being treated in Sacramento remain unchanged.
Catherine Curran, a spokeswoman for Shriners Hospitals for Children Northern California, said Tuesday that 3-year-olds Alejandra Guadalupe Esquer Ochoa and Hector Manuel Robles Villegas were in critical condition.
A third child, 2-year-old Javier Alexis Pacheco Fontes, was in serious condition.
The doctors treating the toddlers said in a statement the children have responded to surgery and are doing well but face a lifetime of rehabilitation, further operations and long hospital stays.
Some parents have complained there were no fire alarms or sprinklers at the converted warehouse in an industrial area of Hermosillo. The building had only one working emergency exit.
2 Officials Whose Wives Own Day Care Center Quit
Meanwhile, two state government officials whose wives own the center said they are resigning from their posts to facilitate the investigation into the blaze.
Antonio Salido, finance director for Sonora state's infrastructure department, said he has stepped down along with Alfonso Escalante, the assistant secretary for livestock.
Salido said the day care center strictly followed safety rules established by the Mexican Social Security Institute, which outsourced child services to them.
He said the day care in the northern city of Hermosillo where a fire on Friday killed 44 children had three emergency exits.
KCRA contributed to this report.