Several hundred fish were killed or left dying Thursday afternoon along the Delaware Canal in Falls Township.

According to Pennsylvania Department of Environmental Protection spokesperson Virginia Cain, depleted oxygen levels in the canal water caused the fish to die off. What caused the oxygen levels to dip so low remained under investigation as of Thursday evening.

The dead fish seemed to be concentrated between Tyburn Road and Wheatsheaf Lane, said a Bristol man who emailed LevittownNow.com Thursday afternoon.

Cain said investigators from the state DEP found oxygen levels in the canal in Falls were at zero.

According to the U.S. Geological Survey, an oxygen-deficient situation in bodies of water can be caused by a number of factors. Often, a body of water’s oxygen enters through a feeder stream, groundwater runoff and the atmosphere.

The investigation into the cause of the low oxygen levels was suspended Thursday evening, Cain told LevittownNow.com.

Delaware Canal State Park rangers were planning to open the gates in Yardley to ” allow cold, oxygen rich water from the Delaware River into the canal. Doing this will introduce oxygen to the system and should relieve stress on the fish,” Cain said.

Dead fish taken for samples will be sent to a lab for testing.

A determination on whether the investigation into the die-off will be made Friday morning.

Officials from Falls Township, the Pennsylvania Department of Environmental Protection, the Pennsylvania Fish and Boat Commission and the Pennsylvania Department of Conservation and Natural Resources, which oversees the canal from Easton, Northampton County to Bristol Borough were along the canal are investigating the fish kill.