The Beijing-Shanghai high-speed train service was brought to a halt for nearly two hours on Sunday night, just 10 days after the link's high-profile launch.
The G151 service, bound for Shanghai Hongqiao, came to an emergency halt while travelling south through Shandong province, due to a power cut that state media claimed was caused by thunderstorms.
Another 19 trains were affected, with passengers on the stricken train complaining of being stranded in hot, dark carriages without air conditioning for upwards of two hours.
There were no injuries reported in the incident, but coming so soon after the 310km/h train service's launch it has rekindled concerns about safety first prompted by reports of massive corruption under disgraced former railways minister Liu Zhijun.
Internet users criticised the train's safety record on online forums and on Weibo, the mainland's answer to Twitter, with some questioning whether a thunderstorm could be responsible for the power cut.
There was also confusion over just how long the train was left without power, with an apparent contradiction between the official statement and eye-witness accounts.