HONG KONG—As floodwaters surged into a stalled subway coach beneath the Chinese town of Zhengzhou, Pure Li hurriedly tapped out farewell messages to a shut buddy on her smartphone. “I may perhaps not be able to get out,” she wrote.

The 26-calendar year-old engineer was one particular of far more than 500 travellers trapped all through the night hurry hour Tuesday, as torrential rains pummeled the central province of Henan. A dozen persons would not make it out alive, authorities say, and at least two had been nonetheless lacking as of Saturday early morning.

Desperate photographs from commuters surrounded by roiling drinking water went viral on Chinese social media this 7 days, putting a nerve in a country that has vastly expanded its subway units, and endured a collection of really serious underground flooding incidents that have elevated security alarms.

On Thursday, China’s Ministry of Transportation requested subway units nationwide to re-analyze and enhance contingency options for excessive temperature. Authorities in Zhengzhou, Henan’s money town, and Zhengzhou Metro Group, the state-owned subway organization, did not answer to requests for comment.

As rain fell in Zhengzhou on Tuesday, turning roadways into quickly flowing rivers and wreaking hundreds of millions of bucks of harm, according to state media, drinking water began to pool in a coach garden, the metro organization explained in a assertion. It then broke via a wall and flowed into a tunnel.