BEIJING — Dozens of workers were crushed to death under an avalanche of scaffolding, cement and steel rods in southeast China on Thursday after a platform in an unfinished tower of a coal power plant collapsed.

The platform, part of a power plant project near Fengcheng, a city in Jiangxi Province, crumpled around 7 a.m. when more than 70 workers were on the site, safety inspectors at the scene said. By early Friday, rescuers had found 74 dead, according to Xinhua, a state-run news agency. Two other people were injured.

As is typical after big industrial accidents in China, government officials promised to find the cause of the disaster and prevent a recurrence. Yang Huanning, the director of the State Administration of Work Safety, was rushing to the power plant, about 750 miles south of Beijing, to oversee the rescue efforts, his office said.

“Strengthen oversight and preventive measures,” the prime minister, Li Keqiang, said in instructions about the accident issued on the central government’s website. “Prevent such major accidents from recurring.”