A train carrying Sen. Dan Sullivan and other Republican members of Congress to their retreat in Greenbrier, West Virginia, has hit a truck with one person reported dead.

Sullivan, the only member of the state's congressional delegation on board, issued a statement Wednesday afternoon.

"I was on board, but was not injured," Sullivan said. "I extend my thoughts and prayers to the victims and their families, and offer my sincere appreciation for our first responders -- who were quickly on scene to assist those in need."

Sullivan's spokesman, Matt Shuckerow, said about 250 GOP members of the House and Senate were on board the train at the time of the collision.

"It's certainly a sad moment, a tragic moment, and he's ultimately grateful for the first responders," Shuckerow said.

Sen. Jeff Flake (R-Ariz.) told reporters he was on the train and helped one of three occupants of the truck, who died at the scene.

The White House released a statement about the accident early Wednesday afternoon: "The President has been fully briefed on the situation in Virginia and is receiving regular updates. There is one confirmed fatality and one serious injury. There are no serious injuries among members of Congress or their staff. Senior Administration officials are in regular contact with Amtrak and state and local authorities. Our thoughts and prayers are with everyone that has been affected by this incident."  

The specially chartered Amtrak train departed Union Station in Washington, D.C. at about 8:30 a.m., and the train hit the back of a garbage truck at about 11:20 a.m. in Crozet, Virginia. The impact threw train passengers from their seats, but so far, lawmakers appear not to have sustained major injuries. Many are also traveling with their spouses and staff. 

Rep. Bruce Westerman, R-Arkansas, told CBSN in an interview that as far as he knows, "Everyone on the train is fine." Westerman was still on the train during the interview. He thought the train was still operable.

Another lawmaker told CBSN that some members jumped from the train to offer help to the people in the truck who were injured. 

Rep. Jeff Denham, R-California, tweeted a photo of damage to the front of the train.

President Trump is meeting with his national security team but is aware of the accident, White House press secretary Sarah Sanders said.

Amtrak released a statement on the incident that said the train "came into contact with a vehicle that was on the tracks at 11:20 a.m. in Crozet, Va. There are no reported injuries to passengers or crew members. Local law enforcement is investigating the incident and crews are inspecting equipment for damage."

The front half of the truck was crushed in the accident.

Highway and rail crossing incidents have increased in recent years. An Federal Railroad Administration report found that the increases were likely due to higher traffic volumes. According to a recent report from 2010-2014 there was an average of 2,100 incidents per year of these collisions between trains and vehicles.

Vice President Mike Pence is scheduled to address the retreat this evening. 

Read more about this story on CBSNews.com.