Complaints came from South of Market, among other places.
Complaints came from South of Market, among other places. Caroline Cutler/Public domain

It did not come from a gas leak.

It did not come from the refinery.

It did not come from the sewer system.

But it came from somewhere. Around 2 a.m. on Wednesday morning, residents of San Francisco started calling the city’s gas company and fire department to report a terrible smell. It was one of those rotten eggy, sulfurous smells that often indicate a gas leak.

The investigation by the local gas company, PG&E, did not find any gas leaks, though. And as KQED reports, no one else would take responsibility for the smell, either. “More than a half-dozen city and federal agencies, Pacific Gas and Electric and the city’s garbage collector say they don’t know what caused it,” the station reported.

San Francisco is not the only city to be blanketed with mysterious foul smells in the past week, it turns out. Philadelphia was subject to its own sulfur-smelling cloud late last week. In that case, though, the source was eventually found—it was coming from refinery across the river that has lost its power and as a result had some “flaring and odor” problems.