Narrative:

After completing a turn to the downwind leg at cma we observed a twin engined cessna pass 300 to 500 feet in front of us and approximately two hundred feet above us; [and] at a ninety degree course to our direction of flight. At no time were we informed that there might be traffic in our area.

Google
 

Original NASA ASRS Text

Title: A C-180 pilot reported an NMAC with a twin engine Cessna while turning downwind in the pattern at CMA. ATC had provided no traffic advisories prior to the event.

Narrative: After completing a turn to the downwind leg at CMA we observed a twin engined Cessna pass 300 to 500 feet in front of us and approximately two hundred feet above us; [and] at a ninety degree course to our direction of flight. At no time were we informed that there might be traffic in our area.

Data retrieved from NASA's ASRS site as of April 2012 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.