Rescue officials in Bangladesh said on Monday they were unlikely to find more survivors in the rubble of a factory building that collapsed last week burying hundreds of garment workers in the country's worst industrial accident.

Heavy cranes were being used to lift huge concrete blocks from the wreckage of Rana Plaza, where 385 people are now confirmed to have been killed according to the latest official toll. The building housed factories making clothes for Western brands.

Hundreds more of the mostly female workers who are thought to have been inside the building when it caved in last Wednesday remain unaccounted for. A fire overnight further hampered the last desperate efforts to find survivors.

"We are giving the highest priority to saving people, but there is little hope of finding anyone alive," army spokesman Shahinul Islam told reporters at the site.

As anger continued to mount over the disaster, the 60-year-old father of the building's owner was arrested on Monday. His son had been arrested by police commandos on Sunday, apparently trying to flee to India.

About 2,500 people have been rescued from the wrecked building in the commercial suburb of Savar, about 30 km (20 miles) from the capital, Dhaka.

Late on Sunday, sparks from rescuers' cutting equipment started a fire in the debris as they raced to save a woman who may have been the last survivor in the rubble. Her body was recovered on Monday afternoon.

"We could not save her, even though we heard her voice this morning," a tearful rescue worker told reporters at the scene.

ARRESTS AND PROTESTS

Officials said the eight-storey complex had been built on swampy ground without the correct permits, and more than 3,000 workers - most of them young women - entered the building on Wednesday morning despite warnings that it was structurally unsafe.

A bank and shops in the same building closed after a jolt was felt and cracks were noticed on some pillars on Tuesday.

Eight people have been arrested over the disaster, four factory bosses, two engineers, building owner Mohammed Sohel Rana and his father Abdul Khalek. Police are looking for a fifth factory boss, David Mayor, who they said was a Spanish citizen.

Rana, a local leader of the ruling Awami League's youth front, was shown on television being brought to Dhaka in handcuffs after he was seized in the border town of Benapole by the elite Rapid Action Battalion following a four-day manhunt.

Khalek, who officials said was named in documents as a legal owner of the building, was arrested in Dhaka on Monday. They face charges of faulty construction and causing unlawful death.

The collapse was the third major industrial incident in five months in Bangladesh, the second-largest exporter of garments in the world behind China. In November, a fire at the Tazreen Fashion factory in a suburb of Dhaka killed 112 people.

Such incidents have raised serious questions about worker safety and low wages in the poor South Asian country, which relies on garments for 80 per cent of its exports. The industry employs about 3.6 million people, most of them women, some of whom earn as little as $38 a month.

In a development that may raise questions about the authorities' handling of the rescue operation, a spokesman at the British High Commission on Monday confirmed that an offer of technical assistance from Britain had been declined.

Anger over the disaster has sparked days of protests and clashes, and paramilitary troops were deployed in the industrial hub of Gazipur as garment workers took to the streets again on Monday, smashing cars and setting fire to an ambulance.

The unrest forced authorities to shut down many factories, which had reopened on Monday after two days of closures. Police fired teargas to disperse protesters.

The main opposition has called for a national strike on May 2 in protest over the incident.

Emdadul Islam, chief engineer of the state-run Capital Development Authority, said last that week that Rana had not received the proper construction consent for the building, and had illegally added three storeys to the original five. – Reuters