Workers prepare to move a charter bus after it was struck Tuesday by a freight train, right, in Biloxi, Miss. The train pushed the bus about 300 feet down the tracks. Authorities said four people were killed and 40 injured.

BILOXI, Miss. — A freight train crashed into a bus full of Texas tourists visiting Gulf Coast casinos, killing four in Biloxi, Miss.

Forty people were hurt, seven critically. The cause of the Tuesday afternoon crash was under investigation.

Witnesses told Mississippi news outlets the bus appeared to have been stuck on the tracks when it was hit. The crossing is on a steep embankment and has a sign warning drivers that it has a low ground clearance.

Authorities on the scene said it took more than an hour to get everyone aboard the bus out of the wreckage. Two people had to be removed with metal-cutting equipment. The CSX Transportation locomotive pushed the bus about 300 feet before coming to a stop with the mangled bus still straddling the tracks.

Police chief John Miller said he was unsure why the bus was stopped on the tracks.

“We don’t know if there were mechanical issues or what was taking place,” he said.

Miller said 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.

The weeklong trip was organized by a senior citizens’ center in Bastrop, Texas, about 30 miles east of Austin. Some passengers boarded in each city Sunday. They also were supposed to visit New Orleans and then return home Saturday.

The names of the dead were not immediately released.

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.