Police detained eight unlicensed welders Tuesday in connection with Monday's deadly apartment fire in Shanghai that left 53 people dead and at least 70 injured, city officials said.
Investigators believe that the welders may have been using their equipment improperly, sparking a blaze that engulfed a 28-story building in the heart of the sprawling Chinese metropolis.
About 17 people remain in critical condition, said Shanghai Deputy Mayor Shen Jun. Family members were reportedly scouring local hospitals for any information on missing loved ones, and aiming their frustration at authorities.
"It is hard to believe the government now. The drills on TV are successful, but when a fire truly happens, it's just useless. We feel helpless," a woman who gave only her surname, Liu, told the Associated Press. Her mother lived on the ninth floor of the building and died in the fire.
Chen Fei, director of the city's firefighting bureau, said the blaze erupted on the building's 10th floor.
Survivors either had to scamper down stairs or descend scaffolding that surrounded the tower. The apartment block, which housed 440 people, was undergoing renovations to add insulation at the time of the fire.
Firefighters facing difficulty reaching the upper levels set up hoses on top of an adjacent building to finally contain the blaze, which raged for more than four hours.
Rescuers were seen carrying survivors out of the building. Earlier attempts to airlift people off the roof with helicopters had to be called off because of thick smoke.
One resident said he and his wife climbed down to safety on the scaffolding from the 23rd floor, where their apartment was, according to the Xinmin Evening Post, a local newspaper.
The man, who identified himself as a retired teacher with the surname Zhou, said he was napping when he was awakened by smoke. He said he rushed through his front door into the hallway and uncoiled a fire hose to extinguish flames next to a window by a stairwell. He and his wife were then able to flee, the newspaper said.
Another survivor, Li Xiuyun, 61, said she hurried down stairs inside the building with her husband, son and granddaughter from their home on the 16th floor, cutting her feet on shattered glass along the way.
"The smoke was very strong and the glass from the windows was scalding," she told the Agence France-Presse news service.
"My son took off his socks and soaked them with water, and we used them to cover our noses. I stumbled on people on the floor when walking," she said at one of the nine hospitals that took in victims.
China's minister of public security, Meng Jianzhu, rushed to Shanghai and called for a thorough investigation through the State Council, the country's Cabinet, the New China News Agency said.
Although China has been undergoing a construction boom for many years, building safety has remained controversial.
Last year, firefighters could do little to stop a massive blaze in a nearly completed Beijing skyscraper housed in the same complex as China's state television headquarters. The building, slated to be a luxury hotel, burned after being set alight by an illegal fireworks show.
Critics also point to substandard construction practices as a major source of safety problems.
They cite the collapse of thousands of buildings, including many shoddily built schools, during the deadly 2008 Sichuan earthquake as a prime example of the poor construction common in much of China.
The following year, a nearly completed 13-story apartment tower in Shanghai toppled, killing one worker in a high-profile incident that attracted stunned onlookers for days because the building remained largely intact on its side.
Chinese have come to call buildings constructed poorly for the sake of cutting costs "tofu dregs," a reference to the mushy curds left behind in the tofu-making process.
Tommy Yang of The Times' Beijing Bureau contributed to this report.