Bacterial contamination was being blamed Monday for an outbreak of foodborne illness following the popular Burger & Beer Bash in Westchester County earlier this month.

The county Health Department said Monday that the campylobacter bacterium was to blame for the outbreak at the June 6 outdoor food festival at the Kenisco Dam in Valhalla.

The bacterium was identified through tests on samples from several people who got sick at the event. The department did not specify exactly how many people were sickened.

But health officials have not determined the source of the bacteria, since most attendees ate food from many of the 30 different vendors at the event, the department said. The department has launched an investigation and has been interviewing people in an effort to trace the source.