About 125 Occupy protesters are snarling traffic Center City with a march to mark May Day.
After marching from Market Street to the Rittenhouse Square area, the demonstrators doubled back to the area around 16th and Market Streets.
On the 1600 block of JFK Boulevard, police warned the protesters would be arrested if they did not disperse.
Deputy Police Commissioner Richard Ross said, "The primary concern right now is to make sure people who work in Center City get home safely."
Two people were arrested after they lay down in front of a bank on the 1600 block of Walnut Street. Police commanders in the meantime ordered all available police vans to Center City for possible mass arrests.
The day's theme was "Strike the Banks" and the march began on Market Street west of City Hall with protests outside branches of Wells Fargo Bank and Bank of America.