BUFFALO, N.Y. — Several lawmakers want the board that runs Niagara Falls’ wastewater treatment plant to resign after a sewage-smelling discharge blackened the water near the base of the falls during a busy tourist weekend.

Members of the Niagara County Legislature’s Republican majority said Thursday they also want the New York attorney general, county district attorney and the Environmental Protection Agency to investigate for possible criminal charges. An investigation by the state Department of Environmental Conservation already is underway.

The legislators complained they have received little information about an incident that had the potential to damage the county’s $827 million-a-year tourism industry.

“Residents deserve to know how this happened, why this happened and exactly what this disgusting discharge was,” Niagara County Legislator Rebecca Wydysh said during a news conference. “We also need to be assured that it will never happen again.”

The Niagara Falls Water Board has said the Saturday afternoon discharge occurred during routine maintenance of a sedimentation basin and contained permitted amounts of accumulated solids and carbon residue. It has apologized for alarming residents and tourists.

Board Chairman Dan O’Callaghan read a brief statement outside the board’s offices late Thursday saying “possible human error or a possible mechanical malfunction” may have occurred. He said he could not elaborate because of the investigation.

Board executives didn’t immediately respond to the legislators’ resignation calls.

“The last time (Niagara Falls) got this much attention, Nik Wallenda was walking across a tightrope, and that had a massive positive economic impact on the region,” Legislature Majority Leader Randy Bradt said. “We can only imagine the damage done to tourism-related businesses due to this mismanagement by the water board.”

The DEC has said the discharge, which enveloped the dock of the popular Maid of the Mist tour boats, violated state water quality standards by changing the color and odor of the Niagara River. Additional findings have not yet been released.

U.S. Rep. Brian Higgins has asked the EPA to investigate whether the release violated the federal Clean Water Act, Boundary Waters Treaty or other international agreements. The river and falls straddle the U.S.-Canadian border.

Canadian authorities did not respond to requests for comment.

The EPA told The Associated Press that the DEC investigation would encompass both state and federal interests.