City Hall announced that large swaths of Center City, and First Ward, and "other areas" were le without electricity in a Tweet just before 9 a.m.
Fire officials identified a substation blaze as the cause of the blackout at around the same time. Residents who come to an intersection with a disabled traffic light should treat it as a four-way stop sign, the fire department added.
Utility company PPL's online power outage map showed as many as 21,000 Allentown residents without electricity at around 9 a.m., WFMZ reported.
City officials said they were working with PPL to fix the issue but said they did not know when power would be restored.
At around 10 a.m., Allentown School District officials said they would dismiss students by 10:30 a.m. due to the blackout.
By 1 p.m., PPL's outage map showed no significant outages in Allentown, though city officials had not issued an update.
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