She was one of eight children who lived in the home and two other kids -- ages 14 and 5 -- remain in the hospital on Wednesday evening.
Heavy flames broke out on the top floor of the three-story home on Astor Street just after 1:30 a.m. Wednesday.
Good Samaritans from a nearby store rushed into the home after hearing two children were trapped in one of the rooms.
They tried multiple times to get in but were turned back by the heavy flames.
"We noticed smoke down the street, we walk down to see what's going on," store clerk Christopher Evans said. "We noticed the flames coming out, so me and the Spanish guy and I banged on everybody's door, the mechanic was trying to wake everybody up, get them out, get them out! And a little boy came out, he's a regular customer here, and he says, 'Help, that's my house!'"
They tried but failed to reach a third-floor bedroom. Firefighters and police arrived and got everyone out of danger.
According to the Essex County Prosecutor's Office, three children were rushed to area hospitals.
The 9-year-old girl was pronounced dead at University Hospital.
The fire is now under investigation by the prosecutor's office.
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