Police detained eight people Tuesday in connection with Monday's blaze at a high-rise apartment building that left 53 people dead and more than 70 injured in Shanghai's Jing'an District, authorities said Tuesday evening.

An initial investigation has blamed the disaster, one of the deadliest in decades, on unlicensed welders, said Zhang Renliang, chief of Jing'an District Government, said at a press conference.

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

Deputy district chief Li Weiping said 15 of the injured were still critically ill as of 4 p.m..

The blaze erupted on the north side of the 10th floor of the 28-story building, said Chen Fei, director of the city's fire-fighting bureau.

The 85-meter-high building housed more than 156 households with 440 people. Residents moved 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 after lunchtime.

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

The city's emergency response center received a fire report at about 2:15 p.m. and authorities dispatched 122 fire engines and more than 1,300 fire-fighters to the site.

More than 100 residents were rescued and the blaze was extinguished by 6:30 p.m..

Local authorities are still trying to determine how many residents were in the building when the fire broke out and the number of missing people.

Police and fire-fighting authorities have promised to disclose more information about the cause of the blaze as soon as possible.

Horror scenes

The entire building was engulfed in the fire and smoke for hours, with flames bursting out of the windows and cracking glass, witnesses said.

The scaffolding netting that enveloped the building quickly burnt and part of the iron structure turned red in the fire.

Among the residents were many retired teachers and some elderly people were in the building when the fire occurred as young people were at work.

Website pictures showed many residents climbing on to the scorched scaffolding, hesitating whether to jump.

A woman surnamed Lu thanked rescuers for carrying her 95-year-old father out of the building Monday. She also expressed gratitude to the local government for accommodating residents of the building in an adjacent hotels.

A man surnamed Wang said he ran all the way up and down twice to search for his wife and finally pulled her out of a burning room.