Five swimmers at Silver Lake in Hollis, N.H. got sick during July. Now, four of the five have been confirmed as victims of Shigella. All the swimmers have recovered.

Health officials Monday were out on the lake taking water samples and test results have found the Shigella bacteria are present. More testing is underway, but in meantime swimmers are being warned about the potential for contamination.

Shigella symptoms include diarrhea, fever and stomach cramps starting a day or two after being exposed. Anyone who swam in the lake recently and who are experiencing those symptoms are urged to seek immediate medical care.