PORTLAND, Ore. (KOIN) — Those visiting Vancouver Lake for the July 4 holiday weekend are being told to stay away from the water again.

A warning was originally issued to park-goers on June 2 when officials said routine testing showed “elevated” levels of E. Coli in the water, which can cause serious illness if swallowed. On Monday, follow-up testing revealed the bacteria again, health officials told KOIN 6 News.

The lake is still under a beach warning and more testing is scheduled for Tuesday, officials said. If Tuesday’s results show no elevated levels of the bacteria, the warning will be lifted.

Health officials are also monitoring an ongoing “harmful” algae bloom at Vancouver Lake, but toxin levels haven’t reached high enough to warrant an advisory, according to the Clark County website. Regardless, changing weather and lake conditions can alter toxin levels during a bloom.

Pet owners are also being told to keep their furry friends from the water. Officials said small children are also at risk on the swim beach as they are more likely to accidentally swallow water.

For more information on what to avoid during a harmful algae bloom, visit the website.

Vancouver Lake Regional Park is still open. Clark County Public Health said water in the park’s restrooms and shelters is not affected and is safe to drink.