* Owner of collapsed building arrested fleeing to India-police
* More than 900 missing, police say
* Four pulled from rubble alive, four days after disaster
By Ruma Paul and Serajul Quadir
DHAKA, April 28 (Reuters) - The owner of a factory building that collapsed in Bangladesh killing hundreds of garment workers was arrested on Sunday trying to flee to India, police said, as fears grew that the death toll could rise sharply with as many as 900 still missing.
Mohammed Sohel Rana, a leader of the ruling Awami League's youth front, was arrested by the elite Rapid Action Battalion in the Bangladesh border town of Benapole, Dhaka District Police Chief Habibur Rahman told Reuters.
Speaking near the site of the wreckage of Rana Plaza, which housed several factories making low-cost garments for Western retailers, junior minister for local government Jahangir Kabir Nanak told reporters that Rana would be brought to Dhaka by helicopter.
Authorities put the latest death toll at 372, four days after the country's worst-ever industrial accident.
Four people were pulled out alive on Sunday and rescuers were working frantically to save several others trapped under the mound of broken concrete and metal, fire services deputy director Mizanur Rahman 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.
Police said one factory owner gave himself up following the detention of two plant bosses and two engineers the day before.
Local news reports said the mother of building owner Rana, who was not being held, died of a heart attack on Saturday evening.
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. On Sunday, however, the roads were quiet.
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, another three 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.
Islam said the building had been erected on the site of a pond filled in with sand and earth, weakening the foundations.
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.