More wastewater has been discharged into the Niagara River in the latest in a series of overflows since a discharge blackened water near Niagara Falls in view of summer tourists.

The Niagara Falls Water Board says heavy and prolonged rain is to blame for Monday morning’s discharge, which again darkened water below the falls on the U.S. side. The board says the rain caused its wastewater system to exceed capacity and overflow with semi-treated wastewater.

The board says the wastewater treatment plant is overdue for upgrades and the board is looking at long-term solutions to its capacity and processing issues.

After a similar discharge last week, state environmental officials called the recurring issues unacceptable. The state imposed a $50,000 fine for the high-profile late July incident.

(AP)