九色

A train derailment that ignited a large, toxic blaze that forced residents near Louisville, Kentucky from their homes for days was caused by a broken bolt, the rail company said this week.

The National Transportation Safety Board has the final say over the investigation but has not determined the cause of the Jan. 16 derailment, said Gary Sease, spokesman for Florida-based CSX Corp. The results of the company’s investigation were reported to the Federal Railroad Administration, he said.

The broken bolt allowed a plate on the 18th car of the 80-car freight train to shift and prevented the wheels from negotiating a slight curve, Sease said.

The derailment, just south of Louisville, involved some cars that were carrying chemicals. The fire, which burned for several days, released toxic smoke and shut down a nearby interstate for half a day.