There were rumors a transformer fire caused the problems. The fire department says that's not the case.
For more than 12 hours PECO has been on the ground and under it at 16th and Sansom Streets trying to figure out the problem that knocked out power to hundreds.
Around 3:30 Wednesday morning, firefighters responded to a possible hazmat situation at the intersection.
There was smoke coming from the site and there was a smell of gas which turned out to be from an unrelated issue.
Residents in the Oakwood Apartments woke up to fire alarms when that smoke creeped into their building.
Lieutenant Bernard Gilliam of the Philadelphia Fire Department explained, "There was smoke filling up in the building. The smoke in the building set off the alarm system."
Philadelphia's Office of Emergency Management says 37 people evacuated the Oakwood Apartments building and were taken to Liberty One to stay warm. Many were allowed back in for a short time to get their belongings.
"You could smell smoke, a little bit like an electrical fire," said Oakwood resident Reid Boothe, "but we didn't feel like we were in danger."
PECO says at the height of the outage 700 customers were without electricity.
By around 2:00 p.m there were 12 properties with meters still in the dark.
That number doesn't sound high, but many of those meters are attached to buildings like Oakwood which has 80 apartments.
Wednesday afternoon we found residents grabbing belongings since the property isn't allowing anyone to return home until the power is back on.
"There's a series of wires that run under this building," said Gilliam. "There's smoke and char down there."
The outages have been spotty, but most of the PECO customers who've been impacted are businesses.
Many of them were forced to close up shop for the day putting up signs to let customers know they were without power.
Late Wednesday night, three customers remained without power including two businesses and Oakwood Apartment.
Oakwood says residents will most likely be out of their homes until tomorrow.
PECO hopes to restore electricity overnight as they found the cables suffered greater damage than originally anticipated.
The cause for what sparked this incident remains unknown.