PHILADELPHIA (AP) — A utility company says a transformer issue is to blame for causing white foam to seep out of a downtown Philadelphia substation and onto a side street this past weekend.

PECO Energy Co. spokesman Ben Armstrong dispelled rumors Monday that an explosion occurred at the substation Saturday afternoon.

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The frothy mess can be traced back to one of the site’s transformers, which flashed momentarily and shut down with an audible popping sound when a circuit breaker went offline.

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Armstrong says the outage triggered emergency systems to flood the substation with fire-suppressing foam. Approximately 2,700 PECO customers briefly lost power.

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A hazmat crew was able to clean up the foam, which isn’t toxic, after a few hours.

An internal investigation is ongoing.

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