DHAKA - At least 21 people were killed and 40 injured in a blaze that engulfed a clothing factory in an industrial town north of the Bangladeshi capital Dhaka, police said.

The fire broke out on the second floor of the Garib and Garib Sweater factory at Gazipur late Thursday, trapping scores of workers who were knitting sweaters for export, fire brigade director Major Sheikh Mohammad Shahjalal told AFP.

"We have brought the fire under control. But we can't say how many have died due to burning or suffocation," he said.

Zahid Hasan, a constable in the police control room, said 21 bodies have been recovered.

Police said 40 people were injured.

Fires due to short circuits and substandard electric wiring are common in Bangladeshi garment factories, annually killing scores of poorly-paid workers who toil 12-14 hours a day in difficult working conditions.

Some 4,500 garment factories accounted for nearly 80 percent of the impoverished country's 15.56 billion dollars (S$316 million) export income in the last fiscal year.