GLENVIEW, Ill. (CBS) — Federal investigators are looking at video of the freight train accident that killed a Glenview couple on the 4th of July.

As WBBM Newsradio’s Regine Schlesinger reports, a video camera on the Union Pacific coal train that derailed on the Glenview-Northbrook border captured the crash.

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LISTEN: WBBM Newsradio’s Regine Schlesinger reports

The Chicago Sun-Times reports investigators think it might help them determine whether a sudden kink in the track caused by the extreme heat contributed to the accident.

Thirty-one of the cars on the 138-car freight train derailed as it was crossing the bridge over Shermer Road at Willow Road around 1:45 p.m. on Wednesday, July 4, spilling a massive amount of coal. The train was hauling coal from Wyoming to Wisconsin at the time.

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Initially, authorities said no one had been injured in the wreck, but crews cleaning up the debris found a bumper on Thursday, and eventually dug out the crushed car, and found the two bodies inside.

The bodies were those of Burton and Zorine Lindner — 69 and 70 years old, respectively – whose car was crushed as they drove under the bridge when it collapsed.

Their son, Robert Lindner, filed a lawsuit this past Friday in Cook County Circuit Court. The family has also retained personal injury attorney Robert Clifford to represent them.

The suit cites alleged negligence in the couple’s deaths.

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Cook County Judge William Maddox last week a request from the Lindner family’s attorneys to temporarily halt cleanup of the wreck, in order to preserve evidence for their lawsuit against Union Pacific.