No cause has been determined yet in the Sept. 15 accident in which 36 cars of a 94-car eastbound Conrail freight derailed near the Temple Street grade crossing.
Bob Sullivan, a communications officer of Conrail, said last week that the investigation is continuing.
The full cleanup costs are estimated in the $2 million to $3 million range, he added.
Steve Johnson of Chautauqua County's Division of Environmental Health said last week that the 20,000 gallons of oil were contained and did not affect the fish in nearby Canadaway Creek.
"Some residue of the oil and the concentrated sulfuric acid is still at the site," he said.
"There is seepage in the ballast of the track bed, and it will take time to work out. The acid has been neutralized with lime," he added.
Temple Street has been opened for several weeks, although some spots show where heavy equipment was brought in. All rail cars have been removed.
The accident occurred on the main Conrail line between the east coast and Chicago.