Four people died and 17 others were taken to a hospital when a train crashed into a parade float carrying wounded veterans in Midland, Texas, late this afternoon.
The float was one of two flatbed tractor trailers carrying wounded veterans and their families to an honorary banquet during Show of Support's Hunt for Heroes parade when a train approached after 4:30, according to officials and witnesses.
The first truck crossed the tracks in time, but the second did not, according to Hamid Vatankhah, a witness who owns a used car lot near the scene of the crash.
Sirens from the police cars in the parade may have drowned out the sound of the approaching train, Vatankhah said.
"Some people were able to jump, and some that were sitting in wheelchairs on top couldn't do nothing about it," Vatankhah added.
Two people died at the scene and two others died at Midland Memorial Hospital, Midland Police Chief Price Robinson said. Of the 17 injured at the hospital, Robinson added, 10 were in critical condition and seven were in stable condition.
Witnesses said the railroad gate did not go down before the floats got to the Union Pacific tracks, according to ABC News affiliate KMID-TV.
However, a Union Pacific spokesman said it appeared safety devices at the crash site were working.
"Our preliminary findings indicate that the lights and gates were working at the time of the incident and that our train crew sounded the locomotive horn," said the spokesman, Tom Lange.
The National Transportation Safety Board was launching a team to the site to investigate the crash. It expected to have investigators at the site this evening and a full team on site by Friday.
Investigators will be able to determine the speed of the train, as well as whether the train's horn was sounded prior to the accident, when they examine the train's black box.
ABC News' Matt Hosford contributed to this report.