SEATTLE - The Metropolitan King County Council has decided to launch its own investigation into what caused major damage at a sewage-treatment plant in Seattle last month.

A news release from the council says members voted unanimously Monday to approve the probe.

Because of the decision, King County administration officials have withdrawn their plans for a separate investigation and instead administrators will work in consultation with the council.

In all, about 235 million gallons of raw sewage and untreated stormwater have flowed into Puget Sound since Feb. 9 when a power outage caused pumps at the facility to fail. The county says about 90 percent of that mixture was stormwater, or runoff that flows off roads. Repairs are estimated to cost about $25 million.

Officials have said they expect to restore the West Point Treatment Plant to normal operations by April 30.