Their mother, however, was nowhere in sight.
Police issued an arrest warrant yesterday for Lorraine Wilson, 31, on charges of reckless endangerment and endangering the welfare of a child.
Wilson allegedly left her children - two boys, ages 4 and 9, and a girl, age 2 - home alone at 1 p.m.
About 5 1/2 hours later, police said, the 9-year-old noticed that his younger brother was playing with a lighter in a second-floor bedroom.
The older boy took the lighter and put it in the bathroom, only to realize that the bed was already on fire.
Police said the boy tried to put out the fire himself. He ran to the back of the house and screamed for help when his efforts failed.
Cops who arrived at the scene broke into the house through a front window and removed the 9-year-old, who had suffered cuts to his hands and feet, and smoke inhalation, while firefighters removed the younger kids, who also suffered smoke inhalation.
Police said the children were treated at Children's Hospital of Philadelphia and released to their maternal grandmother, at the direction of the Department of Human Services.
On Twitter: @dgambacorta