COLUMBUS, Ohio (AP) -- The city of Columbus has spent $723,000 trying to get rid of the rotten taste and smell of its drinking water.

The problems were caused by a mysterious toxic algae bloom in Hoover Reservoir, which serves 500,000 city water customers.

The Columbus Dispatch reports it the city had gotten more than 1,700 complaints about the smell and taste of its drinking water because of the algae.

Matt Steele, Columbus' water supply and treatment coordinator, says the bloom is a mystery, since toxic algae is usually a summertime problem.

Toledo spent $3 million last summer to keep Lake Erie's toxic algae out of the city's drinking water. And in western Ohio, the city of Celina spends about $450,000 a year on algae problems at Grand Lake St. Marys.