Aug. 4 (UPI) -- New York officials are investigating whether an oily sludge discharged into the Niagara River -- that tinted water near the base of Niagara Falls black -- was the result of mechanical or human error.
The leak occurred on the U.S. side of the falls last weekend and images of the smelly scene quickly gained exposure online. Photos and video footage showed a large blob of inky-looking, black liquid pooling near the dock of the Maid of the Mist tour boat, which ferries visitors to the base of the cataracts. Water could be seen streaming into the river from a nearby pipe.
The New York Department of Environmental Conservation identified the source of the discharge as the Niagara Falls Wastewater Treatment Plant.
Officials are now trying to determine whether the leak happened because of employee error, or if a valve malfunctioned and allowed the sludge to flow into the lower Niagara River.
The Buffalo News reported Thursday that officials with the Niagara Falls Water Board, which operates the wastewater treatment plant, said the discharge was part of normal plant operations and has happened numerous times before.
Plant officials said employees empty backflow water into the river so that tanks and filters can receive normal maintenance. However, workers are supposed to stop the flow before the water begins to change color. The remainder of the sludge is vacuumed out of tanks by a contractor.
"Everything that happened is stuff that's always been done in the past," James Perry, the board's administrative services director and human resources manager, told reporters. "The issue is the color. The way it discolored the water was not a usual occurrence. Usually what happens, is they backflush to a certain level, and when the water starts to discolor, they stop pumping."
After hearing officials say that sewage backflow so close to a natural wonder is a regular occurrence, DEC investigators are said to be reviewing the entire plant's operations from top to bottom, the News reported.
Niagara Falls Mayor Paul Dyster said the city's police department has also opened an investigation to determine whether the discharge was the result of criminal wrongdoing.
Some local lawmakers have demanded the resignations of some on the water board.