"The rainwater is continuing to rise and my mobile phone is about to run out of battery. I don't know whether this will be my last post," Ding Xiaopei said in a video on Tuesday evening.

She posted the recording on WeChat, asking for help and showing herself and the many other passengers as they were trapped in flooded subway cars in Zhengzhou, capital of Henan province.

Hundreds of passengers were trapped for hours on Tuesday in flooded subway cars on Line 5 of the Zhengzhou Metro after downpours hit the city. Twelve people died and five were hospitalized, officials reported.

By Wednesday morning, all of the remaining passengers had been rescued.

The record rainstorm caused severe flooding, traffic disruptions and power outages.

Ding, who was able to post another message, was rescued after she and the other trapped passengers experienced fearful, desperate and touching moments.

A woman told China Youth Daily that most passengers did not realize the situation would be so serious when the train made emergency stops from time to time.

"Then the train made another emergency stop between stations and got stuck there. I could see the water rising, and it began to pour into the carriage," she said.

The woman said she saw the water level keep rising, and eventually the level got to people's chests and necks. She felt desperate and began to make arrangements in case of her death.

"I could sense the fear around me in the carriage. There was some turmoil. Someone tried to smash the window, but other passengers stopped him," she said.

"By the time rescuers showed up, the water was at a very high level outside the window. They broke the door and window in the front and pulled passengers out one by one."

Another passenger, surnamed Li, recalled that the stranded passengers had supported each other.

"Men were letting women go first and everyone was making way for any sick or disabled passengers."

Ding finally returned home after midnight, where she found a note her children had left for her, reminding her to drink some water.

"I felt so lucky and blessed to come home," she said.

Qi Xin in Zhengzhou contributed to this story.