What started as a report of an overnight gas leak turned into a three-alarm fire in Center City Philadelphia that burned up apartments and a home.
The explosion and subsequent blaze at 23rd and Naudain Streets led to the evacuation of the 2300 block of Naudain and left at least one person hurt.
Philadelphia firefighters said they first responded to the scene because of a call for a gas leak at a home shortly before 2:15 a.m.
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"Upon the arrival, they obtained a high reading of CO and they recognized that there was fire in the basement," said Deputy Commissioner Richard Davison.
"After the fire had started there was an explosion," said Davison.
More crews were called to the scene because of the explosion that led to a quickly-spreading blaze, according to firefighters.
Medics rushed one woman to the Hospital at the University of Pennsylvania for treatment for fumes.
About two dozen other people were evacuated to the Philadelphia High School for Creative and Performing Arts on S Broad Street where the American Red Cross supplied aid.
In total, about 40 people were forced from their homes including from 11 apartment units and from homes on the south side of the street. A handful of pets also got out OK.
Officers blocked roads in the area as fire crews battled the blaze. PGW crews also responded to the scene due to the gas leak.
It took firefighters a little less than three hours to bring the blaze under control.
Some neighbors in the area called NBC10 to report that they felt or heard an explosion in the area.
Thick black smoke could be seen pouring from the scene. Hours later smoke continued to rise from the partially collapsed ruins that littered the street below.
Firefighters said it could have been worse if someone didn't call 911 when they recognized fumes.
"We're very grateful," said Davison. "That's part of the system, the people, the residents of Philadelphia, to notify the 911 system when they are alarmed about any smell, any incident."
If residents didn't call 911, people might have been in the home when it blew.
Davison said that the fire marshal and PGW would determine if gas caused the home to explode.
The blast also knocked out power including to nearby Albert Greenfield Elementary School forcing the dismissal of the school.