SAN RAFAEL - A person was seen pouring an unidentified substance along a sidewalk at the Northgate One mall in San Rafael, prompting a shelter in place order, according to police.
The San Rafael police department described it as a "hazardous material incident."
Roughly 14 stores at the shopping center were closed Tuesday afternoon, a KTVU reporter saw. That represents about half of the strip mall.
A witness told police the liquid emitted a haze as it was poured from a jug.
One person was treated for chest pains.
Authorities urged others to avoid heading to the area of 234 Northgate 1.
The person seen pouring the substance was identified through surveillance video, but no arrests have been made.
A hazmat team neutralized soil from the planter's box the liquid was poured in and then hauled it away.
KTVU's Tom Vacar contributed to this report.