Zheng Dong, chief meteorologist at the Yantai Marine Environment Monitoring Centre said the ice expanded to 291 square km this week and is continuing to grow.
Zheng said the ice this year is the worst the area has experienced in three years.
Local aqua farmers said the ice is thicker than in years past, which may lead to heavy losses, as the farmers are unable to penetrate the ice to provide adequate ventilation for sea cucumbers and other aquatic organisms.
Coastal police warned that the ice may cause damage to vessels passing through deeper sea areas near the Bohai and Yellow seas, according to a report by state-run Xinhua news agency.