Webber pool in north Minneapolis has been closed more days this summer than it has been open.

The natural swimming pool remained closed Wednesday, the 21st day it hasn't been in use this summer because of contaminated water caused by ducks swimming and depositing fecal matter in the pond and swimming pools.

Minneapolis park staff said bacteria levels were too high to open Tuesday and Wednesday. The pool is always closed on Mondays.

Frustrations were expressed during a staff update at the Minneapolis Park Board meeting Wednesday night. Commissioner Kale Severson, whose district represents the pool, said he was worried about its future.

Park staffers are working to reopen the pool. More samples were taken Wednesday morning, and staff plans to release another update late Thursday morning.

Jeremy Barrick, the board's assistant superintendent for environmental stewardship, said that staff is "putting in a lot of time and energy" in finding a solution to the problem.

The three-year-old, $7 million pool, which uses natural filtering instead of chlorine to clean the water, first closed on June 24. It had reopened for a brief period before being shut down again.