A fourth person has died after Monday's Amtrak train derailment in Missouri, according to the Missouri State Highway Patrol.
In a statement, authorities said that three of the fatalities were passengers on the train and that one had died at University Hospital.
"Law enforcement officials working in conjunction with first responders and Amtrak officials have determined approximately 150 people were transported from the scene to 10 area hospitals for treatment of injuries that range from minor to serious in nature. Amtrak officials stated that there were approximately 275 passengers and 12 crew members aboard the train," the patrol tweeted Tuesday.
Investigators from the National Transportation Safety Board (NTSB) arrived Tuesday at the scene. The agency said it launched a 14-member "go-team" to investigate the accident.
Amtrak Police are providing security to the site, which is located near Mendon.
The Southwest Chief train, which was carrying more than 200 people from Los Angeles to Chicago, slammed into a dump truck. Seven of the train's cars derailed at a rural railroad crossing on a gravel road. The truck was broken into pieces.
The crossing has no lights or other signals to warn of an approaching train.
Passenger Amanda Diehl Drinkard said she heard a crash before the train fell onto its side.
"We heard a big crash and then a big cloud of dirt with a horrible burning oil smell," she told Fox News. "In slow motion the car fell off the rail to the right side. People from across the aisle were falling on top of us. Everyone stayed relatively calm and we managed to push everyone out the top through a broken out window. There were helpful people waiting at the bottom to help down from the car."
Passengers included 16 youths and eight adults from two Boy Scout troops who were traveling home to Appleton, Wisconsin. Fox News has learned that the troops assisted fellow passengers in getting them to safety and provided first aid.
NTSB Chairwoman Jennifer Homendy, who is serving as a spokesperson on the scene, said it was too early to speculate on why the truck was on the tracks and that trains won't run there for "a matter of days" as evidence is gathered.
Homendy is expected to hold a media briefing on the derailment.
Fox News' Lawrence Richard, Garrett Tenney, Louis Casiano and The Associated Press contributed to this report.