Eight people have been detained following a fire in a Shanghai high-rise building that killed at least 53 people, Chinese state media report.
An initial investigation blamed unlicensed welders for starting the fire, Xinhua news agency said. Those held have not been identified.
The block, which housed teachers - many of them retired - was being renovated when it caught fire on Monday.
Public Security Minister Meng Jianzhu has called for a thorough inquiry.
Firefighters battled for several hours to bring the blaze in the 28-storey tower block under control.
Witnesses said the fire started in a pile of construction materials and spread quickly up bamboo scaffolding, setting the whole building alight.
"We detained eight people on suspicion of criminal negligence causing a serious accident," Cheng Jiulong of the Shanghai Public Security Bureau told a news conference.
More than 80 fire engines were brought in and hoses had to be set-up on top of a nearby building to reach the flames.
Chinese TV showed people clinging to bamboo scaffolding surrounding the building as they waited to be rescued.
Mr Meng flew into Shanghai from Beijing in the early hours of Tuesday to guide rescue and relief work.
He urged local authorities to help find those still missing and to ensure the public received up-to-date information about what happened, Xinhua news agency reported.
Mr Meng said lessons should be learned and that an investigation team would report directly to the Chinese cabinet.
BBC Shanghai correspondent Chris Hogg says the minister appeared to be trying to pre-empt concerns of a cover-up or an attempt by those responsible to escape justice.
As the fire took hold, flames could be seen licking the sides of the building, and a thick pall of smoke was visible several miles away.
Some survivors escaped by clambering down the scaffolding, while others struggled down smoke-filled stairwells.
Witnesses reported distressing scenes at hospitals where relatives desperately searched for missing loved ones.
More than 150 families lived in the block. Officials said more than 100 people had been rescued.
Local hospitals said they had treated at least 90 people, some of whom were seriously injured.
Jing'an district government is housing residents affected by the fire in nearby hotels, Xinhua reported.
One of China's commercial hubs, Shanghai has some 20m residents and has seen a frenzy of construction work in recent years.