The strange weird bad smell of unclear origin that had residents causing a stink of their own yesterday is back. They were crying foul in neighborhoods as far apart as the Bayview, the Tenderloin, Nob Hill, the Marina, SoMa, the Mission, and the Outer Sunset and Richmond, but now it's just Tenderloin and Nob Hill residents calling SFPD to make note of the mysterious, sulfurous odor, which KTVU writes is affecting the 800 O'Farrell block and the 900 Mason block near the Fairmont Hotel.

The odiferous events of yesterday had fingers pointing: PG&E said it had nothing to do with the smell, the Fire Department didn't have the answers, and the Coast Guard said no spills in the Bay, that they knew of, had occurred to cause the stench. But now Bay Area Air Quality Management District spokesperson Lisa Fasano tells KQED that a Chevron facility all the way in Richmond could be to blame. β€œWe're investigating the Chevron flaring incident Β… to determine if it could be the potential source,” Fasano said.

Chevron, KQED writes, did not report the flaring incident initially but later acknowledged it had occurred. They don't, however, think they have anything to do with the smell in San francisco

β€œWe experienced some minor flaring,” Chevron spokeswoman Leah Casey said in an email. β€œOur initial investigation shows no connection between the flaring incident and the odors recently detected in San Francisco.”

Jan Null, a meteorologist with Golden Gate Weather Services, also expressed skepticism to KQED. "The distance is about 11 miles and it would have been very diluted," said Null.

And yet, another round of complaints were received by PG&E last night after 11 p.m. hours after a second incidence of flaring at Chevron. The air district is reportedly investigating that incident, too.

One further possibility that KQED floats is that the West Contra Costa Sanitary Landfill is to blame. "There have been odor complaints the last few months coming from the landfill,” Randy Sawyer, the county's chief environmental health and hazardous materials, wrote in an email to KQED. β€œThey have material that is composting and has turned anaerobic. This becomes very odorous.”

Previously: San Francisco Beset By Mystery Stench