One person has died after a chartered train carrying dozens of politicians to a Republican policy retreat struck a refuse truck in a rural town in Virginia.
The White House said one person was killed and another was seriously hurt, while Amtrak said two crew members and two passengers have been taken to hospital with minor injuries.
Politicians said the fatality appeared to be someone who was in the truck.
House Speaker Paul Ryan was on the train and was unhurt, aides said.
Photos from the scene in Crozet, VA pic.twitter.com/qYmIna355K— Bill Cassidy, M.D. (@BillCassidy) January 31, 2018
Oklahoma Representative Tom Cole, who was on the train, said the vehicle had been ripped in half and that emergency workers appeared to be "putting a body away".
Amtrak spokeswoman Kimberly Woods said there were no reported injuries to passengers or crew members after the incident, which happened at around 11.20am local time in Crozet, about 15 miles west of Charlottesville.
Madeline Curott, Albemarle County police spokeswoman, said authorities had received a call "about a fast train hitting a truck".
She would not confirm a fatality but said three people in the truck were seriously injured.
Mr Cole said he felt "a tremendous jolt" when the accident occurred, nearly two hours after the train left Washington heading to the Greenbrier resort in White Sulphur Springs, West Virginia.
The policy retreat, an annual event, is scheduled to last three days and feature speeches from President Donald Trump and Vice President Mike Pence.
Mr Cole said the train stopped quickly after impact.
He said several Republicans who are doctors got off the train to assist, including Ohio Representative Brad Wenstrup, who was also at last June's shooting of Republicans at a baseball practice in nearby Alexandria, Virginia, and treated some of the victims.
First responders, Dr. @BillCassidy and other Amtrak train passengers carry one of the injured to an ambulance after the train collided with a garbage truck in Crozet, Virginia. (photo credit @justinide of the Crozet Volunteer Fire Department) pic.twitter.com/gIbRQWc2b8— Matt Wolking (Text TRUMP to 88022) (@MattWolking) January 31, 2018
North Dakota Representative Kevin Cramer was conducting a live interview with a local radio station when the accident occurred.
"Oh, Jesus, sorry about that, we hit a bump here," he told AM 1100 The Flag, a station in Fargo, North Dakota.
Later, he described the truck's wreckage and said: "Valuable lesson, people. Do not challenge a train at a crossing."
Authorities have not detailed the sequence of events.
Other doctors who helped included Representatives Michael Burgess of Texas, Phil Roe of Tennessee, Larry Bucshon of Indiana, Roger Marshall of Kansas and Louisiana Senator Bill Cassidy.
Mr Cassidy later tweeted that there were three people in the truck and "one is dead".
There were 3 people in the truck that was straddling the track and which the train hit. One is dead. One I am told is being transported but has minor injuries. One has serious injuries—please pray. Laura & I & multiple other physicians tended to the patients until EMTs showed up. https://t.co/qAmoofxakV— Bill Cassidy, M.D. (@BillCassidy) January 31, 2018
White House spokeswoman Sarah Huckabee Sanders said Mr Trump was briefed on the accident.
"There is one confirmed fatality and one serious injury," but no injuries to politicians or their staff, she said.
"Our thoughts and prayers are with everyone that has been affected by this incident," Ms Sanders said.
Kentucky Representative James Comer said about 100 Republican politicians were on the train when the crash occurred, which made him jump out of his seat.
"I looked out the side of the window and then I could see a truck, just in pieces out the side of the window," Mr Comer said.
"It was a garbage truck that was apparently, I would assume, trying to cross the tracks."
Mr Comer said Capitol Police quickly jumped off the train, but came back and asked for any doctors to help.
He said politicians performed CPR on one person.
A Republican aide said the train seemed partially derailed.