People should avoid swimming at Don Carter State Park because of high bacteria levels in Lake Lanier, Georgia state park officials warned this week.

All swimming beaches in Georgia state parks are tested before heavy summer activity begins around Memorial Day, according to Georgia State Parks spokeswoman Kim Hatcher.

Don Carter State Park, located on North Browning Bridge Road in Gainesville, came back with unacceptably high levels of E. coli. The park and beach haven’t been closed, but officials are warning against swimming and wading in the lake at that beach.

Hatcher said on Wednesday that it was the first time swimming had been closed at Don Carter State Park.

“We can’t be sure where this came from because E. coli can come from a number of sources, both human and animal,” she said. “Having to close beaches is rare but has occurred in the past at other parks.”

Another round of tests was performed on Tuesday. Those results will be available Thursday.