NORTHBROOK – A Union Pacific employee spotted a potential problem with a section of track and had called for help just before a freight train derailed in suburban Chicago, killing a couple traveling in their car, railroad officials said.

Union Pacific Vice President of Engineering David Connell told dozens of Glenview and Northbrook residents at an informal meeting Monday that the employee, a signalman, did not think it was of big enough concern to order the freight train to stop. Instead, the employee, who was not qualified to judge the safety of the track, called in an off-duty inspector, but the derailment occurred before the expert arrived.

The Federal Railroad Administration is investigating the July 4 accident, although railroad officials say a preliminary probe indicated that excessive heat caused the track to buckle, derailing 31 cars carrying coal. Most of the rail cars landed in a pile on top of a railroad bridge, causing it to collapse into the street below and crush the car of Zorine and Burton Lindner.