Cambodia has seen a rush of investment in recent years, especially into the shoe and garment sector, with Western and Asian firms attracted by its low-cost labor. The International Monetary Fund says garments account for about 80 percent of the Southeast Asian country's exports.

Ith Sam Heng, minister of social affairs, told Reuters another six people had been injured in the incident at the plant in the Kong Pisei district of Kampong Speu province, 50 km (30 miles) west of the capital, Phnom Penh.

"We will investigate the case and we will take measures against those involved," he said, meaning anyone who might be held responsible for poor safety standards.

He said no one remained trapped inside the building.

Earlier, a trade union member at the factory had said six people had died in the collapse, which happened at around 8 p.m. EDT. The shoe factory, owned by Wing Star Shoes Co Ltd, a Taiwan company, employed about 7,000 people but only about 100 worked in the single-storey warehouse, according to staff.

Work at the plant stopped after the accident.

A Reuters reporter saw footwear bearing the name "Asics" scattered around the damaged warehouse, where a bulldozer was clearing away rubble.

A spokeswoman for Japanese sportswear maker Asics Corp said the factory made running shoes for it. "Our prayers go out to the families of those who have died," she said.

Asics relies on sports shoes for about two-thirds of its sales, which amounted to 57.33 billion yen ($560 million) company-wide in the year to March 31, 2013.

POOR CONDITIONS

A series of deadly incidents at factories in Bangladesh, the world's biggest exporter of clothing after China, has focused global attention on safety standards in the booming garment industry there.

An eight-storey complex of factories housing garment manufacturers collapsed in Bangladesh on April 24, killing more than 1,100 people. That has sparked campaigns in the West to improve safety conditions at plants in the country supplying Western brand names.

Strikes over pay and poor working conditions are common in the sector in Cambodia, also home to numerous factories producing clothing cheaply for Western retailers.

Ngeth Phat, 29, who was among those rescued on Thursday, said Wing Star had been open for little more than a year but there had already been two strikes by workers over poor working conditions and low wages she put at $80 a month.

"After I got into work, bits of brick dropped on me, and about 10 minutes later the whole ceiling collapsed. It was completely dark and I was under other people," she told Reuters from a hospital bed in Phnom Penh.

Ou Sam Oun, the governor of Kampong Speu province, said the factory would provide compensation of $5,000 to the families of the people who had died and $1,000 each to workers who were injured.