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MIDLAND, Texas -- Federal investigators say the warning signals at a railroad crossing in West Texas were activated before a parade float crossed the tracks in an accident that killed military veterans.

National Transportation Safety Board member Mark Rosekind made that announcement at a news conference Saturday. He said the signals had been activated seven seconds before the float crossed the tracks.

Four veterans of Iraq and Afghanistan were killed Thursday when a freight train slammed into the parade float in Midland. Sixteen people were injured.

Rosekind said the NTSB reconstructed the accident using video cameras from the train and a sheriff's vehicle.

He said the train started sounding its horn nine seconds before it hit the float. The train engineer also used the emergency brake five seconds before the crash.