CITY HALL (CBS) — Protesters in Center City burned an American flag, and according to an official, it appears officers were injured during a skirmish.

SEPTA Transit Police Chief Thomas Nestel III tweeted that a “skirmish broke out” at Broad and Cecil B. Moore and that “it appears officers were injured.”

Nestel added that order was restored and that the suspects were taken into custody. Police say officers were sprayed with black spray paint and pepper spray by protesters. 12 officers were sprayed and three suffered injuries.

A nearby Bank of America was also vandalized.

Four protesters were arrested.

Earlier, the protesters blocked JFK Boulevard in front of the Philly Municipal Services Building. At one point, protesters lit an American flag on fire.

They also set on fire other items in the middle of the street.

The protests have caused gridlock as demonstrators march down Broad Street.

The protesters are calling for reforms to the criminal justice system.

They want Mayor Jim Kenney to end the police department’s “stop and frisk” policy.

The protesters are also concerned about how President Donald Trump will fight crime.