A freight train smashed into a charter bus in a coastal Mississippi city on Tuesday (US time), pushing the bus 100m down the tracks and leaving at least four people dead, authorities said.
Rescuers spent more than an hour removing passengers, cutting through the bus's heavily damaged frame to extract the last two.
The bus could be seen straddling the tracks, with a CSX Transportation locomotive pushed up against its left side. The bus was apparently stopped on the tracks when the 52-car train, pulled by three locomotives, slammed into it, said Biloxi Police Chief John Miller.
"We're not sure why," Miller said. "We don't know if there were mechanical issues or what was taking place."
Miller said passengers on the Echo Transportation bus had come from Austin, Texas, carrying passengers to one of Biloxi's eight casinos.
Ameet Patel, senior vice president of regional operations for Penn National Gaming, owner of Hollywood Gulf Coast Casino in Bay St. Louis and Boomtown Biloxi Casino, said the bus was traveling from the Hollywood casino to the Boomtown casino at the time of the crash.
"It's a terrible tragedy," Miller said.
"I know there's a lot of families that are going to be impacted here."
There were conflicting reports of the number killed in the crash. Officials initially said four people died and then revised it down to three. But Vincent Creel, a spokesman for the city of Biloxi, later said after consulting with the coroner's office that four were killed.
Creel emphasized it's a "very fluid situation."
"Any time you have a major incident like this, the information can change," he said.
The names of the dead have not been released.
The bus was carrying people on a trip organized by a Texas senior center. A flier for the tour says some passengers boarded Sunday in Austin, Texas, and others boarded about 30 miles east in Bastrop, Texas.
Michelle Crowley of the Biloxi fire department said 40 people were injured; of those, seven were in critical condition.
A woman who lives about a block from where the train and bus finally came to a stop after the train crashed into the bus says she heard a "loud boom" and knew immediately what had happened.
Cecelia McDonald said she ran out of her house and saw a scene of carnage.
Witnesses told the Sun Herald of Biloxi that the bus was stuck on the tracks for about five minutes before he saw the train hit it. Mark Robinson said some people were getting off the bus as the driver tried to move it, and at least one person was shoved under the bus when the train hit.
A nearby car was used as a stepladder after the crash to get people off the bus, and emergency workers pulled passengers through windows.
Robinson said he thinks the train track, which is on an embankment, poses safety issues.
In addition to bells, warning lights and crossing arms, the crossing has yellow signs warning drivers that it has low ground clearance.
"It's too steep there," Robinson said.
Biloxi Fire Chief Joe Boney says rescuers needed one hour and four minutes to clear everyone from the wreckage. Two people had to be cut out of the bus.
Creel, the city spokesman, said 48 passengers and the driver were on the bus; a bus manifest had listed 50 passengers but two of them did not make the trip.
Medical workers from a hospital blocks away set up a triage area at the scene, and helicopters carried some of the passengers to other hospitals.
The train was headed from New Orleans to Mobile, Alabama, at the time of the crash, said CSX spokesman Gary Sease.
He said the train crew was not injured. The single track is the CSX mainline along the Gulf Coast, passing through densely populated areas of southern Mississippi.
Federal Railroad Agency records show 10 trains a day typically use the track, with a maximum speed of 45 mph.
Records show there have been 16 accidents at the crossing since 1976, including in 1983 and 2003, each of which involved one fatality. A delivery truck was also struck at the same crossing in January, WLOX-TV reports. No one was injured in that crash.
The bus was marked as belonging to Echo Transportation, which Texas corporate records show is a unit of a company called TBL Group, based in Grand Prairie, near Dallas.
"We can't confirm anything at this point," said Elisa Fox, a lawyer for the bus company.
"We're trying to mobilise to assess the situation."
Federal Railroad Administration spokesman Marc Willis said the agency is sending three inspectors to investigate, while Mississippi is sending one. The National Transportation Safety Board said it is also investigating.