A fire official and media reports say the roof of a five-story cement factory being constructed in Bangladesh has collapsed, killing at least four people and trapping many others.

Fire official Mizanur Rahman says the accident occurred Thursday at Mongla in Bagerhat district when about 150 workers were on duty. He says at least 30 people were rescued from under the debris and up to 40 are feared trapped.

Rahman said many of the survivors were injured and have been hospitalized.

The area is about 135 kilometers (85 miles) southwest of the capital, Dhaka.