In this July 29, 2017 photo provided by Rainbow Air INC., black-colored wastewater treatment discharge is released into water below Niagara Falls, in Niagara Falls, N.Y. The water near the base of the falls that border the U.S. and Canada turned an alarming shade of black before tourists' eyes following a foul-smelling discharge from a nearby wastewater treatment plant. The water board for the city says Saturday's discharge was part of routine maintenance of one of its basins, that the discharge was within permitted limits and had dissipated by Sunday. (Patrick J. Proctor/Rainbow Air INC. via AP)

In this July 29, 2017 photo provided by Rainbow Air INC., black-colored wastewater treatment discharge is released into water below Niagara Falls, in Niagara Falls, N.Y. The water near the base of the falls that border the U.S. and Canada turned an alarming shade of black before tourists' eyes following a foul-smelling discharge from a nearby wastewater treatment plant. The water board for the city says Saturday's discharge was part of routine maintenance of one of its basins, that the discharge was within permitted limits and had dissipated by Sunday. (Patrick J. Proctor/Rainbow Air INC. via AP)

NIAGARA FALLS, N.Y. (AP) — The water near the base of Niagara Falls turned an alarming shade of black before tourists’ eyes following a foul-smelling discharge from a wastewater treatment plant.

The water board for the city of Niagara Falls, New York, says Saturday’s discharge was part of routine maintenance of one of its basins.

Video taken from a helicopter shows black-colored water along the Niagara River’s U.S. shoreline below the falls that border the country and Canada. The inky water enveloped the dock for the popular Maid of the Mist tour boats.

Officials say the blackish water contained accumulated solids and carbon residue but no organic oils or solvents. They described the odor as “normal sewer water discharge smell.” The board says the discharge was within permitted limits.

The black water dissipated by Sunday.