Enfield — The New Hampshire Department of Environmental Services yesterday issued a warning that elevated levels of cyanobacteria have been measured in Mascoma Lake.

DES in a news release advised lake users to avoid contact with the water in areas where lake water has a surface scum or blue-green flecks, and advised pet owners to keep their pets out of any waters that have a surface scum or blue-green or bright green flecks.

Conditions vary on the lake, with some portions free of scum sightings while other areas have small blue-green clumps in the water. Recent sightings report congregations of the blue-green clumps on the lake's east edge.

Terri Lynch, president of the Mascoma Lake Association, said last night she had not been aware that DES had issued the warning, and had not noticed any unusual appearance of the condition the state described.

"It's nothing that I have heard of, and I'm on the lake quite a bit," Lynch said.

According the DES Web site, "Cyanobacteria are natural components of water bodies worldwide, but blooms and surface scums may form when excess phosphorus is available to the water. Some cyanobacteria produce toxins that are stored within the cells but released upon cell death."

Researchers at Dartmouth-Hitchcock Medical Center and elsewhere suspect, but have not yet established, a link between the toxins and Lou Gehrig's disease. A cluster of victims has occurred near Mascoma Lake and Kennedy Pond in Windsor but researchers urge residents not to make too much of early findings.

Yesterday's warning will remain in effect "until additional samples reveal cyanobacteria levels have diminished," according to the release.

Jody Connor, chief water pollution biologist for DES, could not be reached for comment last night.