Police closed down the Church Street station just after 8 p.m. on Sunday.
Businesses and people who live in the area were asked to stay inside as the bomb squad and bomb sniffing dogs checked it out.
Eastbound Market Street was also closed to traffic as officials continued their investigation.
The station reopened just before 10 p.m.
SF Muni- Church Station Shut Down due to Suspicious Package. Delays on the F and J Lines. http://t.co/LpY82gQe3x
— 511 Bay Area (@511SFBay) July 27, 2015