BUCKSPORT, Maine — The Maine Department of Environmental Protection is estimating that 4,000 to 6,000 gallons of a chemical used to make coated paper spilled into the Penobscot River when several train tanker cars derailed in Bucksport on Friday.

And while the chemical is not believed to be hazardous, DEP officials said department staff will monitor the site to determine if any harm to wildlife or aquatic life results from the spill.

Four cars in a 31-car train derailed Friday night on a stretch of Pan Am Railways track near the Bucksport/Orrington town line. There were no injuries in the incident, but at least two of the cars tumbled down the embankment and into the Penobscot River.

Pan Am officials acknowledged Saturday that some materials — described as a type of latex — had leaked from two of the tankers but were hesitant to estimate how much before remaining materials could be pumped out and measured.

On Monday, DEP officials estimated that the two cars leaked between 4,000 and 6,000 gallons of a chemical called kaolin onto the ground or directly into the river. A spokesman for Verso Paper’s Bucksport mill, where the train was headed at the time of the derailment, said kaolin is a type of latex used to make coated paper.

In an email to the Bangor Daily News, DEP spokeswoman Samantha DePoy-Warren said kaolin does not have any specific properties that threaten the environment, according to a Material Safety Data Sheet on the chemical. However, guidelines state that it should be kept out of the water, she said.

Crews have been unable to contain the chemical because it sinks in water and because of the presence of the overturned tankers and the location of the tankers in the river, DePoy-Warren said.

“It does not appear that the rail cars are still leaking,” she wrote. “So far, responders have not observed any immediate impacts to the river other than the visible milky white and blue discoloration.”

Roughly 200 feet of track had to be replaced after the derailment. Cynthia Scarano, executive vice president at Pan Am Railways, said that the track reopened to rail traffic on Monday afternoon. Now, Pan Am will have to work with the DEP and an environmental cleanup contractor to figure out the best way to remove the overturned tankers.

Scarano said the railroad likely will first bring in empty tankers to offload the remaining kaolin as well as the clay slurry in the two other derailed tankers. Cranes then will be used to remove the overturned cars, hopefully by Friday, Scarano said.

DePoy-Warren said the DEP staff will be on hand to monitor the transfer to minimize additional spillage and will later conduct a “complete assessment — including sediment sampling — to determine any impacts and additional cleanup needed” at the site.

Verso spokesman Bill Cohen said Monday evening that the derailment had no impact on production at the mill.