Officials with Kitsap Sewer District 7 said Wednesday a leaky containment valve in an manhole at the Ford Ward Treatment Plant may be to blame for the spill of partially treated digester sludge into nearby waterways last week.

Sarah Lee, a sewer district commissioner, said officials don’t yet know how much sludge leaked from a 40,000-gallon tank at the treatment plant.

The operator at the treatment plant discovered the leaking tank early Friday, but most of the sludge was still in the tank. The initial estimate is that 3,000 to 5,000 gallons of material escaped from the tank.

Lee said the leak was quickly stopped on Friday and a clean-up was launched over the weekend.

Officials discovered on Monday that the sludge leak had not been fully contained on the treatment plant property, and the Kitsap Public Health District has taken samples from nearby  streams and Blakely Harbor to determine the extent of the pollution.

Sewer district officials expect to get results from the tests late Wednesday.

The sewer district notified its neighbors Wednesday that the cleanup is expected to be finished by the end of the week.

The Fort Ward Treatment Plant treats sewage for about 500 customers, including Lynwood Center, Rockaway Beach, Pleasant Beach, Point White and Emerald Heights.