Firefighters and police combed the building after the blaze was brought under control and pulled out six bodies.
"Everything inside the factory has been gutted," a Reuters photographer said.
A fire at Tazreen Fashions Limited in a Dhaka suburb in November killed 112 workers and injured at least 150, a blaze that focused world attention on poor safety standards in the country's garment sector.
Working conditions at Bangladeshi factories are notoriously poor, with little enforcement of safety laws. Overcrowding and locked fire doors are common.
Bangladesh has about 4,500 garment factories and is the world's biggest exporter of clothing after China, with garments making up 80% of its $24 billion annual exports.
Officials in the industry have demanded quick implementation of recommendations to improve standrds in a report that concluded the Tazreen blaze was the result of both sabotage and negligence.
Western clothing brands, including Wal-Mart Stores Inc, have announced tougher measures to ensure safety standards are upheld.