Fire broke out on Sunday in a garment factory that collapsed in the Bangladeshi capital, complicating attempts to find any survivors of a disaster that has killed 377 people.
Fire service officials said the blaze had been started by sparks from cutting equipment used by rescuers.
Police said the owner of the factory, Mohammed Sohel Rana, was arrested on Sunday trying to flee to India, as hopes of finding more survivors from the country's worst industrial accident began to fade.
Rana was arrested by the elite Rapid Action Battalion in the border town of Benapole, Dhaka District Police Chief Habibur Rahman told Reuters, ending a four-day manhunt that began after Rana Plaza, which housed factories making low-cost garments for Western retailers, caved in on Wednesday.
Bangladesh television showed Rana, a local leader of the ruling Awami League's youth front, being flown by helicopter to the capital Dhaka, where he will face charges of faulty construction and causing unlawful death.
Authorities put the latest death toll at 377 and expect it to climb higher with hundreds more still unaccounted for.
Four people were pulled out alive on Sunday after almost 100 hours beneath the mound of broken concrete and metal, and rescuers were working frantically to try to save several others still trapped, fire services deputy director Mizanur Rahman said. One woman was pulled out of debris by rescuers but died, fire service officials said.
"The chances of finding people alive are dimming, so we have to step up our rescue operation to save any valuable life we can," said Major General Chowdhury Hassan Sohrawardi, coordinator of the operation at the site.
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.
Officials said the eight-storey complex had been built on spongy ground without the correct permits, and more than 3,000 workers - mainly 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.
Police said one factory owner gave himself up on Sunday following the detention of two plant bosses and two engineers the day before.
Anger over the disaster has sparked days of protests and clashes, with police using tear gas, water cannon and rubber bullets to quell demonstrators who set cars ablaze.
Garment workers blockaded a highway in a nearby industrial zone of Gazipur on Sunday demanding capital punishment for the owners.
The main opposition, joining forces with an alliance of leftist parties which is part of the ruling coalition, called for a national strike on May 2 in protest over the incident.
Built on a Filled-In Pond
Wednesday's 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, and could taint the reputation of the poor South Asian country, which relies on garments for 80 percent 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.
Emdadul Islam, chief engineer of the state-run Capital Development Authority (CDA), said on Friday that the owner of the building had not received the proper construction consent, obtaining a permit for a five-storey building from the local municipality, which did not have the authority to grant it.
Furthermore, three other storeys had been added illegally, he said. "Savar is not an industrial zone, and for that reason no factory can be housed in Rana Plaza," Islam told Reuters.
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Islam said the building had been erected on the site of a pond filled in with sand and earth, weakening the foundations.
North American and European chains, including British retailer Primark and Canada's Loblaw, a unit of George Weston, said they were supplied by factories in the Rana Plaza building.
Since the disaster, the Bangladesh Garment Manufacturers and Exporters Association (BGMEA) has asked factory owners to produce building designs by July in a bid to improve safety.