Outbreaks of potentially harmful algae are a growing problem in waterways across the United States including Minnesota, according to a new report.

The Environmental Working Group, a nonprofit advocacy organization, used news reports and satellite imagery to track harmful algal blooms. The group found nearly 300 blooms recorded in lakes and rivers in 48 states since 2010.

The report also found that the problem apparently is getting worse. Last year, 169 blooms were reported in 40 states, compared to three in 2010.

Harmful algal blooms, sometimes known as blue-green algae, are technically not algae. They are a single-cell organism called cyanobacteria that can blanket a lake and sometimes look like bright-green pea soup.

Cyanobacteria sometimes produce toxins that can harm fish and marine life. They also are hazardous to humans and animals.

In Minnesota, blue-green algae blooms have been reported in several lakes in recent years, including Lake of the Woods, Carver Lake in Woodbury and Lake Cornelia in Edina.

The biggest contributor to algal blooms is polluted runoff from farms, said Craig Cox, senior vice president for agriculture and natural resources at the Environmental Working Group.