The third train derailment in less than two months in a western Kansas county draws the attention of federal investigators.

The latest happened Tuesday morning near the Trego County town of Collyer. Officials said no one was injured when 23 coal-filled cars of an eastbound 105-car train jumped the tracks.

Investigators believe a mechanical problem may have caused that derailment. But an official with the Federal Railroad Administration says it's also possible that a defect in the rail triggered the air-brake malfunction.

Trego County was also the site of derailments of 41 cars near WaKeeney on November 29 and 22 cars near Ogallah about three weeks earlier. A spokesman for Union Pacific says faulty track contributed to those derailments.