The lake, which is called both Hirsch Lake and Runnemede Lake, is located along Singley Avenue.
Between 300 and 500 carp were found dead in the lake Thursday morning.
It appears that only the carp are being killed - no other plant or wildlife in or around the lake seem to be affected. Officials suspect a pathogen specifically affecting the carp may be responsible for the sudden fish kill.
Biologists are hoping to test the tissue of a living but sickly carp to determine if their speculation of a pathogen being the cause is correct.