NEW ORLEANS (AP) — Paper producer Temple-Inland Inc. took responsibility Wednesday for a huge fish kill on the Pearl River that borders Louisiana and Mississippi, blaming a discharge from one of its paper mills.

In a statement, Austin, Texas-based Temple-Inland apologized “for the impact this issue at the mill has had on the Pearl River.” The company said it is working to remove the dead fish and restore the river’s quality.

Temple-Inland said it shut down its Bogalusa, La., plant immediately on Saturday after tests showed the plant would exceed its allowable output of discharge into the river. The company said it immediately informed Louisiana environmental officials of the problem and began working to restore the river’s water quality.

“We never lose sight that we are members and supporters of the Bogalusa area and apologize for the impact this issue at the mill has had on the Pearl River, its aqua culture and surrounding communities,” Temple-Inland chief executive Doyle Simmons said. “We are working diligently and expeditiously to remove the fish kill and restoring the quality of the river.”

In Mississippi, authorities took action to bring fresh water into the river — and alleviate additional fish kills — by temporarily increasing discharges from the Ross Barnett Reservoir near Jackson. The action late Tuesday by the Pearl River Valley Water Supply District also was designed to dilute pollutants.

Last week, a black substance entered the river near the Temple-Inland plant and hundreds of thousands of fish have since died. The mill remained closed Wednesday.

On Wednesday, the Lake Pontchartrain Basin Foundation said at least some pollution had entered the lake. The foundation said that on Tuesday, a 10-mile long line of white foam stretched from Rigolets Pass to Bayou Banfouca, scattering dead catfish. However, the foundation said oxygen levels in the lake appeared normal.

“It is likely the foam and dead fish were carried by tides in normal lake water and may not indicate that significant polluted water has entered Lake Pontchartrain,” the foundation said in a statement.

Scientists said the fish kill was likely due to a lack of water oxygen stemming from the pollution.

It likely will take several days for the additional discharge at the Ross Barnett Reservoir to reach the affected area of the river, said Trudy Fisher, executive director of the Mississippi Department of Environmental Quality.

The reservoir was created by impounding the Pearl River between Madison and Rankin counties in Mississippi. It was completed in 1965 and has since become a popular place for boating, sailing, camping and fishing.

John Sigman, the water supply district’s general manager, said the increased discharges would have little effect on the reservoir, other than a slight decrease in the water level.

“We will return to normal discharge rates after we are able to determine the effects on the lower Pearl River,” Sigman said.

As of Wednesday, the Mississippi DEQ said the kill stretched 35 miles to 40 miles along the river from Bogalusa to the Mississippi Sound. The agency said that the kill numbered hundreds of thousands of fish and mussels and has endangered species such as the Gulf Sturgeon, Ringed Sawback Turtles and an endangered mussel.

St. Tammany Parish said last Tuesday it was planning to declare a state of emergency and request state assistance for the affected area. Parish officials said drinking water supplies head not been affected.

Health authorities have told people to avoid the river and not eat fish from the river from between Bogalusa and Poplarville, Miss., southward to around Slidell.