The video in the player above is from a previous report.
Eastbound lanes between Delaware Street and Highway 101 were shut down for more than 12 hours Thursday during the clean-up of what was estimated to be 40 gallons of sodium bisulfite.
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The spill was first reported at about 10:45 a.m. and led to the street closures and a shelter-in-place for anyone within a quarter-mile.
Sodium bisulfite causes irritation to eyes, skin and mucous membranes if inhaled, ingested or comes in contact with eyes or skin, police officials said.
The San Mateo County Department of Emergency Management said it is used for water treatment and poses a very low risk.
Sodium bisulfite is slightly corrosive and people are being advised to wash it off their vehicles if they drove through the spill.
The material leaked out of a 330-gallon tank on the back of a San Francisco Public Utility Commission truck that apparently developed a crack while in transit, according to San Mateo Consolidated Fire Department Deputy Chief Robert Marshall.
"(SFPUC) will be doing an inquiry into how the tank cracked and caused the leak and everything but at this time we don't know why," Marshall said.
Shortly after the spill was reported, the nearby Fiesta Gardens International School, which is running summer school classes, sheltered in place before eventually evacuating for the day, Marshall said.