An earthquake of magnitude 6.4 struck Taiwan early on Saturday killing at least 12 people, and injuring 475, at least 92 of whom remain in hospital. Rescuers are searching the rubble of a 17-storey apartment building that collapsed, with some people still known to be missing in the ruins of the complex as night fell, government officials said.

Officials warned that more people than usual could have been in the building as families gathered to celebrate Chinese New Year. There were 96 apartment units in the Golden Dragon Building and 256 registered residents. Late in the day, city mayor William Lai said 5 people were missing there, authorities said.

President Ma Ying-jeou has assured an “all-out effort” to rescue people.

Over 800 soldiers have joined in the rescue effort, with the help of hi-tech equipment and rescue dogs.

Questions were raised about the construction of the Wei-guan Golden Dragon Building in the southern city of Tainan, with its floors that leveled down on each other when the 6.4 magnitude tremor hit at around 4 a.m. (20:00 GMT), at the start of a Lunar New Year holiday.

Among the dead was a 10-day-old girl who was found in her dead father’s arms, media reported.

Rescuers set up hydraulic ladders and a crane to search the ruins, pulling survivors to safety, with hundreds taken to hospital, though many were quickly released.

Rescuers found an 18-year old man alive and conscious shortly after dark, according to Taiwan television. They were working to get him free, while a 30-year-old woman, a nine-year old girl and a male toddler were pulled out alive.

A government emergency center said that buildings in nine other locations in the city had collapsed and five were left tilting at alarming angles.

Fire department official said rescue efforts were focused on the apartment block, where a child’s clothes flapped from a first-floor laundry line and the smell of leaking gas hung in the air.

“I was watching TV and after a sudden burst of shaking, I heard a boom. I opened my metal door and saw the building opposite fall down,” said a 71-year-old neighbor named Chang.

A plumber narrated how he fetched some tools and a ladder and prized some window bars open to rescue a woman crying for help.

“She asked me to go back and rescue her husband, child, but I was afraid of a gas explosion so I didn’t go in. At the time there were more people calling for help, but my ladder wasn’t long enough so there was no way to save them.”

The quake was centered 43 km (27 miles) southeast of Tainan, at a depth of 23 km (14 miles), the U.S. Geological Survey said.

Rescuers dressed in red and yellow overalls pulled over 240 survivors from the ruins and later inserted huge supports under slabs of leaning concrete to buttress the ruins as they searched for more.

Commenting on the collapse, city officials said it was too early to determine if poor construction was a factor in the building’s collapse.

Liu Shih-chung, city government deputy secretary general, referred to the possibility of structural problems related to poor-quality reinforced steel and cement as shown on television footage of the ruins of the commercial-residential building.

The construction and engineering companies that built the complex are no longer operating, records showed.

Two neighbors reported earlier concerns about the construction when the building was going up in the early 1990s.

“I looked at it and thought, only people from out of town would buy there. We local people would never dare,” said one of the neighbors, Yang Shu-mei.

In 1999, a major earthquake in central Taiwan killed about 2,400 people and caused destruction across the island, which lies in the seismically active “Pacific Ring of Fire”.

In a supporting notion, President Ma Ying-jeou visited an emergency centre and hospital in Tainan while President-elect Tsai Ing-wen cancelled appointments to help bring together rescue efforts.