About 100 workers were feared trapped on Thursday when 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 collapsed in the port town of Mongla, 335 kilometres southwest of the capital, Dhaka. The factory is run by a subsidiary of the Bangladesh army

"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.

Bangladesh factory collapse

A Bangladeshi woman attends to her husband, one of the workers injured in the collapse of a cement factory roof, after he is brought for treatment at a hospital in Khulna, Bangladesh, on Thursday. (Shaikh Mohir Uddin/The Associated Press)

Fire official Mizanur Rahman told The Associated Press many of the survivors were injured and had been taken to hospital. The cause of the collapse is being investigated.

In April 2013, a building containing garment factories collapsed in Dharka, killing more than 1,100 people.

With files from the Associated Press