About 10,000 gallons of treated waste water from the Wailua treatment plant overflowed from a manhole Tuesday morning and made its way to an area just outside the fence line of the plant at Lydgate Beach Park, Kauai County officials said in a news release.

The spill occurred sometime after 8 a.m. and was contained by about 8:50 a.m.

The cause of the spill is under investigation by county crews. Preliminary results indicate there is partial blockage of the sewer line leading to the ocean outfall or partial blockage of the ocean outfall, officials said.