About 100 workers are feared trapped after a cement factory collapsed in Bangladesh, a police official told Reuters.

Four people were confirmed dead.

Rescuers also pulled about 40 survivors from the debris after the factory, run by a subsidiary of the Bangladesh army, collapsed in the port town of Mongla, 335 km (210 miles) southwest of the capital, Dhaka.

"There were about 150 people, including workers, inside the factory building when it collapsed," said Belayet Hossain, the officer in charge of the Mongla Port police station near the factory.

Soldiers and sailors were helping firemen to search for survivors, another official said.

"There are more bodies inside the debris. We're trying to recover the living people first," said district administration official Mohammad Abdus Samad.

Bangladesh has a poor record for building safety.

A complex of shops and small factories collapsed in 2013 killing more than 1,130 people, most of them garment workers.

The collapse of Rana Plaza, built on swampy ground outside the capital, Dhaka, ranked among the world's worst industrial accidents and sparked a global outcry for improved safety in the world's second-largest exporter of ready-made garments.