TAINAN: Before their apartment tower collapsed in a Taiwan earthquake at the weekend, a young couple living on the 14th floor had already been given a clue that the building was unsafe.

But it came too late.

Chen Yi-ting and her husband bought the apartment in the centre of Tainan city five years ago, having relocated from an outlying district. They had a small hiccup with the mortgage -- the first bank they approached had declined their loan application without stating why -- but they found another lender and moved in with their infant daughter.

Soon after, according to Chen's mother, one of the couple's friends, who had ties to the first bank, told them that it had a policy of refusing loans to residents of the 17-storey Wei-guan Golden Dragon Building, due to its poor construction.

Now, Chen, 35, and her husband, Lin Wu-chong, 38, are in intensive-care in two separate hospitals in the southern city. She has a cracked skull and he has damaged lungs.

Their seven-year-old daughter is dead.

"People from outside of the town, people like them, had no idea what was going on before they moved in," Chen's mother, Kuo Yi-chien, explained as she waited in a hospital corridor outside the intensive-care unit where her daughter is.

"They did not know the building was completed by the second developer after the first one went bust. They only found out after they signed the contract."

The two-decades-old building is at the centre of rescue efforts after the 6.4 magnitude quake struck before dawn on Saturday, with at least 24 known to have died there and more than 100 still missing deep in the rubble.

It was the only major high-rise building in the city of 2 million people to have completely collapsed. Its lower stories, filled with arcades of shops, pancaked on top of each other before the entire U-shaped complex toppled in on itself.

Sixty-one-year-old Kuo said residents of the building had long complained of many problems before the quake, such as tiles falling from walls, malfunctioning lifts and blocked pipes.

The couple paid 3.5 million Taiwan dollars ($105,000) for the apartment.

"We are simple minded people. We did not think it (the initial loan refusal) might have been for some other reason," Kuo said.

Tainan's government says the building had obtained its construction permit legally and withstood a much more destructive quake in 1999. Centred in central Taiwan, that tremor killed 2,400 people and caused damage across the island.

"In the city government's record, there was nothing wrong with it," said Wu Chong-rong, chief of Tainan Public Works Bureau.

Hsu Yin-hsuan, an architect hired by Tainan's government to investigate the collapse, said the government had spent money after the 1999 disaster to buttress official buildings so they would be better able to endure future quakes.

But, Hsu added: "Nothing similar has been done to privately owned buildings."

The Wei-guan Golden Dragon building secured its construction licence in 1992 and building was completed in 1994, according to government records.

Two main firms that built the tower, Wei-guan Construction and Da Hsin Engineering, have since gone out of business.

Reuters witnesses at the scene of the collapse saw large rectangular, commercial cans of cooking-oil packed inside wall cavities exposed by the damage, apparently having been used as building material.

This was a problem found in some of the buildings that collapsed in other parts of Taiwan in the 1999 quake. The destruction at that time revealed that cooking-oil cans had been used as filler inside the walls of some buildings.

Tainan Mayor William Lai said he had asked prosecutors to investigate and that the government had hired three teams of civil engineers to inspect the building's structure.

"When it's completed, we'll punish those who should be held accountable," he said.

Seventy-year-old retiree Yang Shu-mei, who lived next to the building, said she had witnessed its construction and that she and other neighbours had always doubted the workmanship.

"When it was being built, I looked at it and thought, only people from out of town would buy it. We local people would never dare to," she said.