BOULDER, Colo. -- Tubers are being asked by the Health Department to stay out of Boulder Creek because they are concerned about a high level of bacteria in the water.

Samples taken from Boulder Creek revealed levels of E. Coli were four times greater than what they should be.

County Health officials that monitor the water said swallowing the bacteria-infested water can cause fever, stomach aches and nausea. Open sores can also cause problems.

"In the case of a wound you can get it infected and we have seen some pretty serious infections come out of the creek from people who were playing around and had an open cut," said environmental health planner Lane Drager.

Boulder Creek is not an official recreation spot like the Boulder Reservoir. If high levels of bacteria were detected in the reservoir, it would have to be closed to swimmers.

There are several reasons for the pollution in Boulder Creek.

"Some of the potential sources are septic systems along the creek, pet waste, wildlife that recreates in that area and any urban sources runoff," said Drager.

Some people said they aren't worried because the water looks clean. Experts said don't be fooled because you can't see bacteria. They said they do expect the bacteria levels to go down as the temperature cools.