No injuries were reported.
A tanker containing liquid sulfur caught fire in the derailment and firefighters decided to let it burn because dousing it with water could wash the chemical into the nearby Little Elkhart River, Harp said. The fire was still ablaze late Tuesday afternoon and Harp said it was expected to burn until at least noon Wednesday.
As many as three other cars may be leaking material, but Indiana Department of Environmental Management spokesman Rob Elstro said because of the fire and unsafe air immediately nearby it was impossible to assess the potential environmental damage. He said there could be an impact to nearby water that feeds into the Little Elkhart River and a marshy area adjacent to the railroad.
"Once we're able to get closer and do a full environmental impact we'll know more," he said.
Elstro said authorities couldn't immediately determine what was in the leaking cars because there's a big pileup and it was hard to tell the cars apart from a distance. He said a tanker carrying the gasoline additive toluene that was derailed was removed safely without leaking.
Forty-three of the train's 59 freight cars were loaded, according to Norfolk Southern spokesman Dave Pidgeon. Crews used heavy trucks to lift the derailed cars back onto the track.
Foam was spotted in the nearby water so booms to contain any leaking material was put out as a precaution, Elstro said. He said it wasn't known if the foam was natural or caused by leaking material.
Authorities evacuated people from six homes downwind of the derailment, Harp said. Many in the area are farmers so the homes are spread apart. Harp said crews were regularly checking the air quality in the area. He said by late Tuesday afternoon the air was safe about 100 yards away from the burning car. He said no decision has been made on when people will be allowed back in their homes.
Inah Schrock, who lives in a farmhouse along the tracks just southeast of the crash site, said she didn't hear the derailment but woke up with police and firefighters in front of her house. She said she wasn't worried because police told her she should be safe.
"They told me we should be OK with the wind direction," she said.
More than 300 Amtrak passengers traveling to Chicago were briefly stranded in Ohio as the derailment closed the tracks along the way.
Amtrak spokesman Marc Magliari said two trains waited for three hours in Toledo. The Lake Shore Limited from New York and Boston has since been rerouted through Michigan and passengers on the Capitol Limited from Washington were transferred to buses.