The crash happened around 3:30 p.m. on the Bingaman Street Bridge between South 4th Street and the interchange with the West Shore Bypass in southwest Reading.
Initial reports from the scene were that four people, including the police officer, were seriously injured.
All were taken to Reading Hospital for treatment.
Deputy Chief Mark Talbot told WFMZ-TV that the officer was responding to a call at the time of the crash.
The Bingaman Street Bridge, which crosses the Schuylkill River and connects south Reading with the bypass and Lancaster Avenue in southwest Reading, is closed to traffic in both directions.
Talbot said he expects it to remain closed into Friday evening.