Mystery Odor Causes City to Order People Inside Vallejo, California, later lifts order, but cause of smell still a mystery By Newser Editors and Wire Services Posted Sep 21, 2016 10:59 AM CDT 17 comments Comments File photo of a shipyard in Vallejo, Calif. (AP Photo/Eric Risberg) (Newser) – It smelled so bad in Vallejo, California, overnight that the city ordered people to stay inside. The shelter-in-place order has since been lifted, but the cause of the nasty odor is still a mystery, reports the San Francisco Chronicle. For now, the best bet is that it comes from an oil slick reported in nearby San Pablo Bay, and the US Coast Guard is currently trying to find the slick and determine if it's the cause. The smell was so sickening that several residents went to the hospital. Vallejo authorities have ruled out a gas leak, notes KNTV, which reports that the first call to authorities came in Tuesday evening.