* More than 900 still counted as missing, police say
* Four pulled from rubble alive, four days after disaster
* Owner of collapsed building on run, border authorities alerted
Hope for survivors under the rubble of a building that collapsed outside the capital of Bangladesh faded on Sunday, and with more than 900 people still counted as missing fears grew that the death toll could rise far beyond the latest figure of 363.
Four people were pulled alive from the wreckage of the Rana Plaza, which housed several factories making low-cost garments for Western retailers, four days after the country's worst-ever industrial accident.
Rescuers worked frantically through the morning to release several others who fire service Deputy Director Mizanur Rahman said were trapped under the mound of broken concrete and metal.
"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 remains of the building in the commercial suburb of Savar, about 30 km (20 miles) from the capital, Dhaka.
Officials said the eight-storey tower had been built on spongy ground without the correct permits, and more than 3,000 workers - mainly young women - had been sent in 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.
The owner of the building, identified by police as Mohammed Sohel Rana, a leader of the ruling Awami League's youth front, was still on the run. Airport and border authorities have been alerted to prevent Rana from fleeing the country.
Police have also detained several of his relatives to compel him to surrender and to find out where he might be. Local news reports said his mother, who was not being held, died of a heart attack on Saturday evening.
Anger at the negligence sparked days of protests and clashes, with police using tear gas, water cannons 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 Saturday 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.
"Only CDA can give such approval," he said. "We are trying to get the original design from the municipality, but since the concerned official is in hiding we cannot get it readily."
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.