Experts say unusually high phosphorous levels in Lake Auburn caused a fish-killing algae bloom last year, but what caused phosphorous levels to spike remains under investigation. A team of water quality experts and engineers hired by the Lake Auburn Water Protection Commission to investigate the fish kill team gave an initial report Wednesday night at Lewiston City Hall. The Sun Journal, reports that engineers say the high phosphorus levels could have been caused by runoff from the lake’s feeder streams and ponds or by a new species of alga, or a combination of the two. They also are trying to determine whether the bloom was an isolated event or a troubling trend, and how to stop it happening again. The bloom last September killed an estimated 200 trout.