The six-storey buildings collapsed in Wenzhou's Lucheng industrial district and rescuers were verifying the number of people trapped under the debris.
Seventeen people were confirmed dead, local govt officials said.
Earlier today rescuers pulled out six people alive from under the debris, state-run Xinhua news agency reported.
Rescuers said the buildings that collapsed were built by villagers themselves. Five adjacent houses built in the 1970s remain standing, but rescuers demolished them to avoid any chance of secondary accidents.
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According to Zhou Liqiang, who has been living nearby for over 10 years, the victims were mainly migrant workers.
Survivor Yan Yongfa, 57, said he shared one room with four other workers and their boss rented the room for them.
Each room in the collapsed building used to have two to three tenants, the report cited Yan as saying.
The cause of the collapse was under investigation.
In May, 16 people were reported dead after a residential building in Guizhou province in the southwest collapsed due to landslides.
Two people were killed and 24 injured in April when a storm brought down a wholesale market building in Foshan city, in the southern province of Guangdong.