San Francisco police are investigating two letters containing a suspicious substance that were received at a building near United Nations Plaza this afternoon.

Police responded to the building, located in the 1100 block of Market Street, which is near 7th Street, after being alerted about the letters at 3:14 p.m., police spokesman Officer Albie Esparza said.

Investigators remained at the scene as of about 4 p.m. trying to determine the nature of the substance, Esparza said.

No injuries have been reported, he said.

Dan McMenamin, Bay City News

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