About 100 people were inside the cement warehouse under construction in the port city, 200 kilometers (125 miles) southwest of the Bangladeshi capital, Dhaka, when its roof collapsed.
More than 40 people have been rescued and some have been taken to hospital.
Building standards in Bangladesh have always been low.
More than 1,130 people were killed in the 2013 collapse at Dacarana Plaza. Most of the victims worked in the clothing industry.
The disaster was one of the world's worst industrial accidents.
In Bangladesh, officials say many bodies are still buried in the debris of a collapsed cement plant. "We are trying to save the living first," regional official Mohammad Abdul Sama told Reuters.
浙公网安备33010802003254号