A city official for the first time is revealing a rise in cancer among firefighters who served at Ground Zero, The Post has learned.

Dr. David Prezant, the Fire Department's chief medical officer, has found that firefighters who dug for victims at the World Trade Center are getting cancer at a higher rate than firefighters before 9/11 -- and some types of cancer are "bizarrely off the charts," say sources briefed on the seven-year, federally funded study.

Prezant discussed the findings with members of a WTC medical-monitoring committee last month, several attendees said.