Bangladesh's government is investigating allegations the sole emergency exit was locked at a garment factory where a fire killed seven women.

The blaze on Saturday (local time) at the Smart Export Garment factory in Dhaka happened just two months after a blaze killed 112 workers in another factory, raising questions about safety in Bangladesh's garment industry, which exports clothes to leading Western retailers. The gates of that factory were locked.

Government official Jahangir Kabir Nanak said an investigation had been ordered into the cause of the weekend's fire and allegations the emergency exit was locked.

Altaf Hossain, father of a worker killed in the latest fire, has filed a police case against three directors of the factory, accusing them of negligence involving the fire, Dhaka Metropolitan Police sub-inspector Shamsul Hoque told The Associated Press.

He said police had begun an investigation.

Doctors said most of the victims died from asphyxiation.

"When I tried to escape through the emergency exit I found the gate locked," factory worker Raushan Ara was quoted as saying by Dhaka's Prothom Alo newspaper.

The newspaper said at least 50 people were injured in a stampede triggered by the fire, and six of them were hospitalised.

Some of the injured jumped out of the windows of the two-story factory, survivors said.

Dhaka Metropolitan Police deputy commissioner Monzurul Kabir said the bodies of seven women were recovered from the top floor of the factory.

He said the factory was making pants and shirts, but could not provide further details.

Fire official Abdul Halim said it took firefighters about two hours to bring the blaze under control.

Volunteers joined firefighters in battling the fire as a large crowd gathered outside the factory awaiting word on the fate of relatives. Family members were seen crying near the body of a female worker named Josna, who was 16.

About 250 workers were working at the time of the fire, newspapers said.

It was not immediately known if the factory produced garments for any international companies. The owner was not available for comment, and the Bangladesh Garment Manufacturers and Exporters Association said the factory was not a member so it had no details.

Earlier this month, Wal-Mart Stores alerted its global suppliers that it would immediately drop them if they subcontract their work to factories that had not been authorised by the discounter.

The stricter contracting rule, along with other changes to its policy, come amid increasing calls for better safety oversight after the deadly fire in late November at a factory owned by Tazreen Fashions, which supplied clothing to Wal-Mart and other retailers. Wal-Mart has said the factory was not authorised to make its clothes.

Wal-Mart ranks second behind Swedish fast fashion retailer H&M in the number of clothing orders it places in Bangladesh.

Fires have caused more than 600 deaths of garment workers in Bangladesh since 2005, according to research by the advocacy group International Labour Rights Forum.

- AP