Unlicensed welders have been detained by police in China after a blaze engulfed a high-rise apartment building under renovation in Shanghai, killing 53 people and injuring more than 70 others.
A preliminary investigation showed the four men improperly operated their welding equipment, sparking the blaze in China's business capital, state television and media websites reported.
Witnesses and building residents quoted earlier by state media said the fire began when building materials caught alight. The flames then spread quickly to scaffolding covering the 29-storey building, which houses a number of retired teachers as well as other families.
Apart from the death toll of 53, the city government said more than 70 other people had been rushed to hospital.
While some survivors were housed overnight in the gym of a nearby retirement home, others searched for missing family members.
Some residents escaped by climbing down scaffolding which had been put up for the renovations.
The fire was one of China's worst in recent years, and disasters of this scale are rare in Shanghai, a wealthy city which is one of the country's best-run urban centres.