CHICAGO, IL - U.S. Sen. Dick Durbin is urging railroad companies to conduct frequent track inspections to prevent rail derailments resulting from heat-related track buckling.

The Illinois Democrat's remarks during a Sunday press conference come as investigators continue to examine the cause of a July 4 train derailment that killed two people.

A Glenview husband and wife were crushed by the wreckage of a Union Pacific freight train derailment that caused a suburban Chicago railroad bridge to collapse. It sent train cars crashing onto the couple's car on the road below.

Union Pacific officials believe the 100-degree heat that day may have caused a rail to expand and led to the derailment.

Durbin wants rail companies to investigate track areas prone to that kind of heat-related buckling, sometimes called "sun kinks."