Swimming at Chatfield State Park has been reopened but remains closed at Cherry Creek State Park due to elevated E. coli levels in the water.

Park employees have put up signs at the park entrances, along the beach at and other areas at Cherry Creek to let people know. Colorado Parks and Wildlife employees said routine water-quality testing Thursday showed that levels of the bacteria at both parks were above levels considered safe by state health officials.

But CPW spokeswoman Kara Van Hoose said that swimming resumed at Chatfield after water samples collected and tested Friday passed Colorado Department of Public Health and Environment standards.

The public can monitor conditions at the parks through their websites and CPW Northeast Region Twitter account will announce when Cherry Creek’s swim area will reopen.

“While these closures are not common, we test the water often to make sure the public is safe while enjoying the reservoir,” said Cherry Creek State Park Operations Manager Larry Butterfield said in a statement.

Butterfield said the high bacteria levels can be caused by fecal waste from wildlife, run-off from urban areas, or excessive run-off from rain. The park has received heavy rainfall this year.

Although the area is closed to swimming, beach access and other water-related activities, like fishing and paddle boarding, are allowed.

CPW notified the CDPHE and the Environment and the Jefferson County Health Department of the test results.