Cambodian clothing industry workers have been killed in the partial collapse of the shoe factory where they worked, adding to the loss of life in the Asian industry of making garments for the west.

A concrete ceiling fell in at the Wing Star Shoes plant in Kampong Speu province, west of the capital, Phnom Penh, authorities said. Police officer Khem Pannara said heavy equipment stored above may have caused the collapse.

Authorities told the Associated Press that two bodies had been pulled from the wreckage and at least seven people were injured, while a union official speaking to the Reuters news agency put the death toll at six or more. There were estimates of up to 50 people trapped in the wreckage.

"We were working normally and suddenly several pieces of brick and iron started falling on us," said an injured 25-year-old Kong Thary, recounting the scene from a nearby clinic.

Pannara said it was unclear how many people remained trapped.

The garment industry is Cambodia's biggest export earner. In 2012 more than $4bn worth of products were shipped to the United States and Europe.

About 500,000 people work in more than 500 garment and shoe factories throughout the country.

The Phnom Penh Post, a daily newspaper, reported on 22 March that workers from the Wing Star plant had stopped work and blocked a main road for about an hour in a protest over wages and working conditions.

The accident comes about three weeks after a building collapse in Bangladesh that killed 1,127 people in the global garment industry's deadliest disaster. Bangladesh is the third-biggest exporter of clothes in the world, after China and Italy.