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CASSELTON, N.D., Dec 31 (Reuters) - Tests of air over a small North Dakota town shrouded in smoke from a fiery oil train crash show that the pollution level is dropping and residents who were evacuated might be able to go home soon, authorities said on Tuesday.
The 106-car BNSF Railway Co oil train struck a derailed grain train on Monday afternoon about a mile (1.6 km) west of Casselton, triggering explosions and fire that sent a plume of thick, black smoke over the town of 2,300 people.
No injuries were reported. About 65 percent of the town some 25 miles (42 km) west of Fargo was evacuated as emergency workers and hazardous materials crews battled the blaze.
Cass County Sheriff Paul Laney said air quality was improving and officials would be discussing when residents could return home.
"Once I can stand up, look you in the eye and say they're safe to come home, that's exactly what we're going to do. We're just not there yet," Laney told a news conference.
Dr. Alan Nye, a toxicologist hired by BNSF to monitor the crash, said particulate levels were falling, with repeated tests in what he called the "good range."
He said the tests had not shown byproducts from burning crude oil.
"I would say it's all about where you are in the wind and how close you are, but I would be happy if my neighborhood air quality was as good as the readings we got later on this morning," said Nye, a partner with the Center for Toxicology and Environmental Health in Little Rock, Arkansas.
SMOKE FROM WRECKAGE
Laney told CNN earlier on Tuesday that 10 to 12 cars were still burning. Officials had no update on the number although smoke could still be seen coming off the wreckage.
Jan Sinner, a manager at the Days Inn hotel, said the air was clear and appeared normal.
"It's fine. If you cross the railroad tracks, you wouldn't even know anything had happened," she said.
The crash was at least the fourth major explosive derailment this year involving a train hauling oil. It is certain to fuel more debate over additional safety measures to address the oil-by-rail boom.
They include tighter rules on highly flammable types of crude or costly retrofits of tank cars. More than two-thirds of North Dakota's oil production is shipped by rail.
Yet in the state, the center of the shale oil revolution and the origin for most U.S. oil-train shipments, there was little immediate outcry.
The impact of the incident is more likely to be felt thousands of miles (km) away, along the densely populated coastal regions such as the Pacific Northwest, where some residents have raised alarm over the potential environmental impact of oil-rail traffic.
"Accidents like this are not only wake-up calls to the residents directly affected, but to those along the heavily trafficked routes bringing crude to the US east and west coasts," said Eurasia Group analyst Elena McGovern.
(Additional reporting by Anna Louie Sussman in New York and Ian Simpson in Washington. editing by Gunna Dickson)