At least nine people living in a nearby town were also injured in the blast when windows shattered, it said.
Among the dead were quarry workers and others who transported and unloaded the explosives, the report said. An earlier report by Xinhua said the explosion had occurred at the cement plant itself.
One Yingde government official, reached by AFP, declined to comment.
The quarry supplies the Hailuolongshan cement plant, which Xinhua said is owned by the listed Anhui Conch Cement Co.
Safety standards are regularly flouted in China, and workplace accidents remain common despite repeated pledges by the government to improve regulations and oversight.
Earlier this month, an explosion ripped through a family-owned lock workshop operating illegally in eastern Zhejiang province, killing 13 people and injuring 14.
In June, explosions ripped through two fireworks factories - at least one operating illegally - killing 14 people and injuring 13 in separate incidents.