There were reports of shots fired on Market Street between Sixth and Seventh Streets around 3 p.m. Thursday, and the subsequent police activity caused a traffic jam as the entire block was closed temporarily. It's unclear who fired any shots, or who was fired on, but the SFMTA reported something about a "possible intruder" on Twitter. The situation apparently also temporarily impacted Muni underground service.

The F-line was backing up and Muni buses were being rerouted onto Mission Street, and back onto Market above Seventh.

We'll update you as we learn more details, and/or when the situation is cleared. Currently the Muni Metro should be functioning properly.

Update: It sounds as though Market Street should be fully open again, though the westbound side of the street was still closed until after 4 p.m. Bay City News reports that two individuals were detained after the report of the shots being fired, a weapon was recovered, and again, there were no injuries reported.