Shiny crude oil residue from the derailed CSX train that lit the James River on fire Wednesday has stretched nine miles downstream, a Virginia environmental official said Thursday.

CSX workers using two massive cranes continued cleaning up the derailed tanker cars from beside the river Thursday. They then planned to tackle the three cars that plunged into the water and set the river’s surface ablaze.

A National Transportation Safety Board team is on site to investigate the cause of the derailment. The 105-car train originated in North Dakota’s Bakken shale region, a booming source of crude, according to CSX, and was headed to Yorktown, Va. There have been increasing concerns about the safety of trains transporting crude following recent high-profile crashes, including one that left 47 people dead in Quebec last summer and another in Casselton, N.D., in December.

According to preliminary information gathered by the NTSB, the train passing through Lynchburg was moving at 24 miles-per-hour when it left the tracks and was engulfed in flames, belching deep black smoke. NSTB spokesman Keith Holloway said some of the train’s cars were classified as DOT-111 tank cars, a widely used type of tanker that has been subject to earlier NTSB safety examinations. Holloway said the age of the DOT-111 cars; whether they met newer, more stringent standards; and whether they were among those cars that derailed are all part of the investigation.

Lynchburg’s water intake on the James River is upstream from the site of the crash and spill, so its water supply was unaffected, officials said.

Brian Coy, a spokesman for Virginia Gov. Terry McAuliffe (D), said “so far, all reports are there has not been impact on drinking water” elsewhere in the state either. The extent of the environmental damage from the spilled crude is still being assessed, he said.

“The key factor here is, How much? How much is left in the cars? There’s still information to collect,” Coy said

Virginia’s Department of Environmental Quality has collected water quality samples, but the analysis will take another day or two, spokesman Bill Hayden said. “At this point we have not seen any impacts on fish or wildlife,” Hayden said.

“The oil was largely contained in the area of the accident, but we have seen a sheen [that] stretched for about nine miles. It’s not very thick,” Hayden said. “It’s an oily residue on the surface of the water…We’ll check and see how far that ends up going.”

Lynchburg officials said the community was getting back to normal routines.

“They are going to try to clean this up as soon as it is safely and humanly possible,” said Lynchburg deputy city manager Bonnie Svrcek. A restaurant beside the crash site, The Depot Grille, was feeding cleanup workers Thursday and was expected to open again to the public Friday, Svrcek said. A nearby children’s museum, Amazement Square, was also shut Thursday following Wednesday’s conflagration, and provided an eerie reminder of the close call.

“Amazement Square is very, very busy place. Many school children come here for end of year celebrations. They come from surrounding counties and from Charlottesville and beyond,” Svrcek said.

CSX said in a statement that it is making “land-, air- and water-based assessments of potential impacts from the derailment” and taking “measures to prevent dispersal of any contents from the train that may have entered the James River.”

Drexel University environmental engineering professor Charles N. Haas has noted that sedimentary organisms may be affected for miles. Whether benzene and other chemicals from the spilled crude could pose a hazard to area residents would depend on their concentrations, he said.

After recent rains, the river “is high and it’s running very fast so it will help mix up small amounts of oil,” Hayden said. “If the water were low, it could collect along the shore and affect things that way.”