Residents of Vallejo were ordered to shelter in place overnight Tuesday as a mysterious odor sickened and hospitalized an unknown number of people. This was shortly before a "sheen" was spotted on the San Pablo Bay that led to a disruption in ferry service Wednesday morning. KRON 4 reports that the roughly 40-yard-wide patch on the water was first seen early this morning, and it led to an investigation to determine if the odor and the sheen were related.

The shelter in place was lifted this morning, and the Vallejo Fire Department managed to determine that the source of the odor was not Vallejo itself. However, no one has yet to figure out what caused the smell — which Bay City News reports was similar to that of natural gas.

According to NBC Bay Area, a majority of phone calls from concerned residents — over 500 — emanated from the Glen Cove and Beverly Hills Park neighborhoods. Patients at local hospitals reported burning in throats and noses.

Meanwhile, the Coast Guard has yet to figure out if the odor is caused by the sheen, or even what the sheen exactly is.

But ABC 7's Laura Anthony posted video to Twitter showing a ship believed to be the source of the slick, whatever it may be, near the Rodeo Phillips refinery.

Ferry service has been restored, but the sheen and the smell persist. However, Bay City News notes that one thing has been confirmed: The odor is neither natural gas nor refinery burn-off. As a general rule, the Vallejo Fire Department yesterday reminded residents that "If you smell gas outside shelter in your home, close windows, turn off air units."

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