* 228 dead, 1,000 injured, toll could go much higher
* Cracks found in building day before collapse - police, industry official
* Canada's Loblaw, UK's Primark say their garment suppliers at site
By Serajul Quadir and Ruma Paul
SAVAR, Bangladesh, April 25 (Reuters) - Survivors from a garment factory that collapsed in Bangladesh killing at least 228 people described on Thursday a deafening bang and tremors before the eight-floor building crashed down under them.
Many more of the mostly female workers were still feared trapped in the rubble more than 24 hours after the disaster, which has brought renewed attention to Western firms who use Bangladesh as a source of low cost goods.
In the evening, local residents were still pulling survivors and bodies from the wreckage of the Rana Plaza building in the commercial suburb of Savar, 30 km (20 miles) outside the capital Dhaka, using crowbars and their bare hands in sweltering heat. More than 1,000 people were injured.
"I thought there was an earthquake," said Shirin Akhter, 22, who was starting her day at the New Wave Style workshop six floors up when the complex crumbled. Akhter was trapped for hours before breaking through a wall. She says her monthly wage was $38.
Relatives identified their dead among rows of corpses wrapped in white cloth in a nearby school field.
Police said the owner of the building, local politician Mohammed Sohel Rana, was told of dangerous cracks on Tuesday.
While a bank in the building closed on Wednesday, the factories told their workers there was no danger, industry officials said. Rana is now on the run, according to police.
"An unspecified number of victims are still trapped," said Mizanur Rahman, a rescue worker with the fire brigade, as he clambered over the wreckage. "We can't be certain of getting them all out alive. We are losing a bit of hope."
Dhaka's district police chief Habibur Rahman said the death toll could rise further.
The government declared a national day of mourning and flags were flown half mast at all official buildings.
Dhaka city development authority had filed a case against the building's owner for faulty construction, police chief Rahman said. It filed another case against the owner and the five garments factories for causing unlawful death.
Bangladesh Garment Manufacturers and Exporters Association (BGMEA) President Mohammad Atiqul Islam said there were 3,122 workers in the factories on Wednesday. He said that local officials had indicated the cracks the day before.
"We asked the garment owners to keep it closed," Islam said.
Rana had told proprietors of the building's five garment factories that the cracks were not dangerous, Islam added. "After getting the green signal from the plaza owner all the garment factories opened," he said.
More than 1,000 textile workers besieged the BGMEA offices on Thursday, pelting it with stones and clashing with riot police, TV channels showed. The workers demanded all garment factories be shut and the owners harshly punished for accidents.
Hundreds of students donated blood at a clinic in Savar after doctors at Dhaka hospitals said they couldn't cope with the number of victims.
Firefighters and troops carried young women survivors of the accident on stretchers, some apparently semi-conscious.
Mohammad Mosharraf, who was rescued on Thursday after 26 hours, said he had been hit on the head by something heavy and knocked unconscious when the building came down.
"When I regain my sense I found another four colleagues are also trapped under the debris of the building," he told Reuters. "We desperately tried to shout for someone to rescue us. Initially we didn't receive any response, but we moved to another part of the floor and found some light and heard voices."
The Rana Plaza building collapse follows a fire at the Tazreen Fashion factory on the outskirts of Dhaka that killed 112 people in November and another incident at a factory in January in which seven people died, compounding concerns about worker safety and low wages in Bangladesh.
Entry level wages in these factories start at 14 cents an hour, said Charles Kernaghan, with the Institute for Global Labour and Human Rights.
UK clothing retailer Primark, which has 257 stores across Europe and is a unit of Associated British Foods, confirmed that one of its suppliers occupied the second floor of the building. Danish retailer PWT Group, which owns the Texman brand, said it used a factory in the building for seven years.
"We check the working conditions at the factory, but we are not construction engineers. We cannot be held responsible for how they build their factories," PWT director Ole Koch said.
British clothing retailer Matalan said it used to be supplied by one of the factories at the complex but had no current production there.
Canada's Loblaw, a unit of food processing and distribution firm George Weston Ltd, said one factory made a small number of "Joe Fresh" apparel items for the company.
Primark, Loblaw and PWT operate under codes of conduct aimed at ensuring products are made in good working conditions.
Documents including order sheets and cutting plans obtained by Reuters appeared to show that other major clothing brands such as Benetton had used suppliers in the building in the last year. A Benetton spokesman said none of the factories were suppliers to the company. Spain's Mango said it had an unfulfilled sample order with Phantom Apparel, at the plaza.
About 3.6 million people work in Bangladesh's garment industry, making it the world's second-largest apparel exporter. The bulk of exports - 60 percent - go to Europe. The United States takes 23 percent and 5 percent go to Canada.
Following the Tazreen fire, giant U.S. retailer Wal-Mart Stores Inc. said it would take steps to alleviate safety concerns, while Gap Inc. announced a four-step fire-safety programme.
Wal-Mart said it had not determined whether a factory in the building that collapsed was producing goods for the company.
Edward Hertzman, a sourcing agent based in New York who also publishes trade magazine Sourcing Journal, said pressure from U.S. retailers to keep a lid on costs continued to foster unsafe conditions.
Hertzman, whose trade publication has offices in Bangladesh, said New Wave Bottoms Ltd occupied the second floor, Phantom Apparels Ltd the third, Phantom Tack Ltd the fourth and Ethar Textile Ltd the fifth.
The New Wave website listed 27 main buyers, including firms from Britain, Denmark, France, Germany, Spain, Ireland, Canada and the United States.