Two train carriages plunged into a river in south-western China on Thursday after floods destroyed a section of rail bridge.
The bridge began to give way as the train was sitting atop it.
But all passengers are believed to have been evacuated before the carriages plummeted into the waters below.
The train cars were swept nearly 700 feet downstream, while the rest of the train remained safely on the undamaged sections of bridge.
Although there have been no reports of injuries or deaths, rescue workers are trying to reach the submerged carriages to ensure that no one is still trapped inside.
China has been ravaged by devastating floods and torrential rains this summer.
More than 2,000 people have been killed so far this year by flooding, landslides, and mudslides.
The cost of the damage has reached into the tens of billions of dollars.