By Brad Edwards

NORTHBROOK, Ill. (CBS) —A Union Pacific railroad employee noticed something potentially wrong with the tracks an hour before the July 4 derailment and bridge collapse in Northbrook that killed two people, railroad officials said Monday night.

The employee, who was checking the tracks, alerted a manager that day, but the pileup occurred before that supervisor could arrive, CBS 2’s Brad Edwards reports.

The information was released as Union Pacific railroad representatives  met with residents at Glenbrook North High School in Northbrook. Railroad officials apologized to the public for the wreck.

The July 4 derailment and bridge collapse killed Burt and Zorine Lindner of Glenview.

UP officials discussed the 2009 derailment near the same location, at Shermer Road; the 2011 repair project and replacement plans for the current bridge.

“While we can’t change what happened, we can learn from it,” David Connell, vice president of engineering at Union Pacific, told an audience of about 200. “We believe we had a heat-related anomaly to the track.”

The Lindners were under the bridge when it collapsed.  It was unknown until the next day that anyone was buried in tons of coal and train cars until a bumper was discovered that belonged to the couple’s Lexus.

Robert Clifford, lead attorney for the Lindner family in the civil action against UP, has called for the National Transportation Safety Board to do an independent investigation into the incident.

The current investigating entities are the Federal Railroad Administration and the UP itself.

There is no definite time-frame to replace the bridge that crossed Shermer Road.