Philadelphia emergency responders have not determined what caused the widespread gas odor people smelled in multiple parts of the city on Monday.
The odor was strong enough that some believed it to be a natural gas leak, which it was not, and it resulted in several Center City buildings being evacuated as a precaution. Reports about the smell started before noon.
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For a time, officials thought the origin was the former Philadelphia Energy Solutions refinery in South Philadelphia. Crews at the refinery property had been cleaning tanks there Monday, and an initial report from the Philadelphia Office of Emergency Management attributed the odor to a non-hazardous chemical release.
However, later in the afternoon, the Philadelphia Fire Department, which was leading the investigation and sent firefighters with the department's Hazmat Task Force to the refinery, said that wasn't the case.
Many Philadelphians took to Twitter to react to the unknown odor in Center City on Monday.
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