Tacloban city disaster management officer Derrick Anido says the fire was caused by a kerosene lamp and quickly consumed the canvass tent after midnight.
The shelter was in a "tent city" in San Jose district, which was wiped out by tsunami-like storm surges and fierce winds from Typhoon Haiyan in November.
Anido says the woman's 7-year-old son, the lone survivor of the fire, is still fighting for his life.