WINTHROP -- State officials continue to wonder how oil is leaking into Annabessacook Lake.

The oil emanating from the old Carleton Woolen Mill seeped into Mill Stream and has been contained at the mouth of the lake.

"The nagging question remains: Where is this oil coming from?" said Tom Benn, remedial project manager for the Department of Environmental Protection. A similar oil spill occurred in 2006.

To try to find out, and to prevent any future occurrence, Benn said the state plans to seal off a large pipe that diverts water from Mill Stream and passes under the old mill complex. The cap on the pipe will be permanent.

Other work will take several weeks to complete. Benn said the state will coordinate its efforts with affected homeowners and business owners.

"All of us are frustrated with the persistence of this problem," he said.

Other action items include:

n Boring 10- to 15-foot holes into bedrock along a retaining wall by the mill, downstream from an old boiler building where oil may have originated, to help determine if oil is contaminating the seams in the rock.

n Sampling sediment from the bottom of Annabessacook Lake in the northern basin, where Mill Stream empties into the lake.

n Moving booms on Mill Stream upstream to reduce the area contaminated by oil.

n Keeping booms on the lake to contain oil until all sampling has been done.

n Possibly removing contaminated streambed soil.

Steve Cartwright -- 623-3811, Ext. 435

scartwright@centralmaine.com