Shanghai police detained eight people Tuesday in the aftermath of Monday's blaze at a high-rise residential building that killed at least 53 people and injured more than 70, officials said.

Relatives of victims from Monday's high-rise building fire in Shanghai burn paper money at the site of the inferno to mourn their family members.

Authorities blamed the fire on unlicensed electric welders who allegedly ignited flammable nylon netting and bamboo on the scaffolding surrounding the building, Cheng Jiulong, a deputy chief of the Shanghai Public Security Bureau, said at a press conference Tuesday.

Some of the welders were among those detained, but the identities of the others were not immediately known.

A total of 15 of the injured, including nine people aged over 50, remained in critical condition as of Tuesday afternoon, Li Weiping, a vice director of the Shanghai Health Bureau said.

About 800 residents who live in three buildings, including the one destroyed by the fire, have been arranged to stay at 16 hotels in the city.

The 85-meter-tall building housed more than 156 households with 440 people. Residents began moving into the building in March 1998 after construction was completed in 1997.The building was undergoing an energy-saving renovation project when the fire started in the afternoon.

Jing'an District Construction Corp and the Shanghai Jiayi Decoration Corp were the contractors for the renovation project.

Renovations were among the projects that were subject to construction restrictions during the World Expo, which ended last month, and most of the work resumed just recently after the ban was lifted downtown.

Hu Zhenqing, a 60-year-old man living on the 20th floor, who was relocated to a nearby hotel, told the Global Times Tuesday that the energy-conservation project was necessary, but since the renovations began he had been keeping a closer eye on his apartment for security reasons.

Residents also complained about litterering cigarette butts left by construction workers.

Monday's blaze casts a spotlight on lax safety standards and insufficient capabilities for fighting fires in high-rise buildings in big Chinese cities, experts said.

In February 2009, a fire engulfed a 159-meter-tall hotel next to China Central Television's lavish new headquarters in Beijing after an unapproved fireworks display went wrong, killing a fireman.