RONKONKOMA - A dangerous and potentially deadly form of algae has invaded Long Island's largest lake.

The blue-green algae, known as cyanobacteria, recently showed up in Mill Pond and Lake Agawam. It has now been found in Lake Ronkonkoma, too.

Experts say the algae can cause liver failure in small children. It could also cause liver cancer over time.

Environmentalists say the algae is caused by untreated sewage seeping into the lakes.

Water tests in Lake Agawam came back with confirmed high levels of toxins, which means the lake contains enough toxins to cause health problems for people and animals.

Tests have been done at Lake Ronkonkoma every day this week. So far, toxin levels remain low.

The beaches along Lake Ronkonkoma reopened to swimmers Friday, but some say they still won't go in the lake.