Rainwater left untreated in cooling towers atop city-owned Harlem Hospital fueled the Big Apple’s deadliest Legionnaire’s disease outbreak in a decade, the Rev. Al Sharpton charged Tuesday.

A new lawsuit is blaming two construction companies for causing the deaths of five people and leaving more than 100 others sick with Legionnaires' disease in Harlem. According to the lawsuit, the companies failed to properly clean storm water from cooling towers at Harlem Hospital.

Two construction workers who claim they contracted Legionnaires' disease while working at or near Harlem Hospital Center are suing contractors they allege failed to safeguard water cooling towers at the building against contamination by the bacteria that causes the illness.

Officials said Monday night there has been an uptick in cases in the Legionnaires' disease cluster in Central Harlem.