At least 30 people have been killed and hundreds are feared trapped after an eight-storey building collapsed in the Bangladeshi capital, Dhaka, emergency services say.
Frantic efforts are under way to rescue those beneath the debris. At least 200 were injured by the collapse.
The army is helping with the rescue operation on the outskirts of Dhaka.
Building collapses are common in Bangladesh where many multi-storey blocks are built in violation of rules.
The eight-storey building contained a clothing factory, a bank and several other shops. It collapsed during the morning rush hour.
Many people have gathered near the scene looking for friends and relatives.
The BBC's Anbarasan Ethirajan, in Dhaka, says that it is not yet clear what caused the collapse but local media reports said a crack was detected in the block on Tuesday.
Police told local media that the rear of the building suddenly started to collapse on Wednesday morning and within a short time the whole structure - except the main pillar and parts of the front wall - had caved-in, triggering all-round panic.
Only the ground floor of the Rana Plaza in Sava remained intact after the collapse, officials said, as army and fire service rescuers equipped with concrete cutters and cranes dug through rubble to pull out trapped people. Many onlookers also joined the effort using their bare hands.
Local police chief Mohammed Asaduzzaman told the AFP that the situation was "disastrous".
Survivors have described their terror as the collapse began.
"I was in the cutting section of the garment factory and suddenly we heard a huge noise and the building collapsed within a few minutes," a garment worker told private Somoy TV.
"I removed the rubble and came out with two other workers. But at least 30 other workers in my cutting section were still unaccounted for," he said.
In November, a fire at a garment factory in a Dhaka suburb killed at least 110 people and triggered a public outcry about safety standards in the industry.
The last major building collapse was in 2010, when a four-storey building collapsed in Dhaka killing at least 25 people and injuring several others.
Bangladesh has one of the largest garment industries in the world, providing competitively priced clothes for major Western retailers which benefit from its widespread low-cost labour.