Three other people were injured, including a person whom rescuers managed to pull from under the debris at the site in Fengcheng city in the southern province of Jiangxi, CCTV reported.
The platform had been built around a cooling tower that was undergoing repairs, according to state news agency Xinhua.
Sixty-eight people were working on the platform at the time of the collapse, according to China’s State Administration of Work Safety.
More than 200 firefighters were deployed, as well as search and rescue dogs.
Images from CCTV showed a pile of twisted metal and dozens of rescue workers searching for victims under the rubble.
In a statement, Chinese premier Li Keqiang called for rescue teams to “work around the clock to save people trapped,” and to “make every effort to treat the wounded and try their best to reduce casualties.”