Shanghai, Nov 16 (IANS) Four people were detained Tuesday over a massive fire in Shanghai that engulfed a 28-storey building and left 53 people dead and over 70 injured, a media report said.

The high-rise building, which housed 156 families of retired school teachers and is situated at the intersection of Jiaozhou Road and Yuyao Road, was being renovated at the time of the incident at about 2.15 p.m. Monday.

Initial investigation into the incident blamed the disaster on "maloperation by unlicensed electric welding workers", Xinhua reported Tuesday citing xinmin.cn.

The blaze was brought under control at 6.30 p.m. after more than 100 fire engines were put into service. Helicopters were sent to rescue people trapped on the roof.

The cause of the fire was still unknown, but an eyewitness said he saw construction material catching fire before the blaze climbed up the scaffolding and spread quickly.

The government has arranged food and accommodation for the fire-affected residents evacuated to nearby hotels.