Police in Bangladesh are investigating the death of a 10-year-old boy at a textile mill who was killed after co-workers inserted the nozzle of a high-pressure air pump in his rectum and turned it on.

The boy, Sagor Borman, worked at a textile mill in Narayanganj, on the outskirts Dhaka, and died on Sunday, police official Forkan Sikdar said.

"The boy died after other workers inserted a nozzle through his rectum. His father found his son lying beside a compressor machine with his abdomen swollen," Sikdar told Reuters on Monday.

Children under the age of 14 are not allowed to work under Bangladeshi law but child labor is common in a country where almost a quarter of its 160 million people live the below poverty line of $2 a day.

Bangladesh relies on garments for about 80 percent of its exports and for about 4 million jobs, and is a major supplier of clothes to developed markets in the West.

Accidents and poor conditions in the textile and garment sector are a major concern for foreign buyers.

The mill where the boy worked produces yarn for garment factories, and about 30 children, aged between 10 and 13, were found there when police raided it on Monday, Sikdar said.

"They have been handed over to their families."

In August, a 12-year-old boy working at a motorcycle workshop was killed in the same way after he had tried to quit his job. In November, a speedy trial court sentenced two people to death for the killing the boy.