The Minneapolis Park and Recreation Board temporarily closed the Webber Natural Swimming Pool on Friday after witnesses said a person put an unidentified white substance in the water, the Park Board said Friday in a news release.

The person who put the substance in the water reportedly made physical and verbal threats and inappropriate comments to people at the pool, according to the release.

The pool in Webber-Camden on the city's North Side uses filters and plants to keep water clean.

The incident is under investigation, and the pool is closed while the park board and other authorities assess the water, the news release said.

Residents are encouraged to use other facilities, including the system's splash pads, pools and water parks and beaches, to cool off while Webber pool is closed.