By Brendan O'Brien
Jan 13 (Reuters) - Eighteen of 20 tanker cars carrying oil that derailed in the fiery crash of two trains in North Dakota in late December were punctured, spilling more than 400,000 gallons of crude oil, safety regulators reported on Monday.
In a preliminary report, the National Transportation Safety Board said that the oil train headed east struck a derailed car from a westbound grain train, leading to the derailment and fire about a mile (1.6 km) outside the small town of Casselton, North Dakota, on Dec. 30.
Both trains were operated by BNSF Railway Co, more than 100 cars long each and were traveling well below the posted 65-mile-per-hour speed limit, the NTSB report said. BNSF is owned by Warren Buffett's Berkshire Hathaway Inc.
The grain train was traveling at 28 mph (45 km per hour) and the oil train at 43 mph (69 kph) when emergency braking systems were applied on both trains, the report said.
A series of powerful explosions and fireballs followed the collision, with the blaze creating plumes of thick, black smoke that passed over Casselton, forcing about 1,400 people in the area from their homes. No injuries were reported.
The incident caused about $6.1 million in damage, according to the NTSB report. A broken axle and two wheels were shipped to the NTSB laboratory in Washington for further evaluation, as were locomotive event and video recorders, the agency said.
The crash came five months after a runaway oil train carrying Bakken crude derailed and exploded in the center of the Quebec town of Lac-Megantic, killing 47 people.
The incident fueled a drive for tougher standards for such shipments, including potentially costly retrofits to improve the safety of tank cars that regulators have cited as prone to puncture.
In early November, two dozen cars on another 90-car oil train derailed in rural Alabama, erupting into flames that took several days to fully extinguish.
The Association of American Railroads recently proposed costly fixes to older tank cars that do not meet its latest standards but continue to carry hazardous fuels such as oil.
The fixes include protective steel jackets, thermal protection and pressure relief valves, which could cost billions of dollars. Oil shippers, likely to be saddled with the costs of retrofits, oppose some of the changes proposed by the association.