Fire broke out this afternoon in a garment factory that collapsed in the Bangladeshi capital, complicating attempts to find any survivors of a disaster that has killed at least 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 today while trying to flee to India.
Hopes of finding more survivors from the country's worst industrial accident are beginning to fade.
Mr Rana was arrested by the elite Rapid Action Battalion in the border town of Benapole, Dhaka District Police Chief Habibur Rahman said, 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 Mr 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 this morning 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 30km 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 today 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 today 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 2 May in protest over the incident.
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.