The death toll of a big fire that engulfed a high-rise building in downtown Shanghai had risen to 53 by 9:20 am Tuesday, local authorities said.

More than 70 people injured in the inferno are being hospitalized.

The 28-story building at the intersection of Jiaozhou Road and Yuyao Road in Jing'an District, a densely-populated area in Shanghai, was being renovated when it caught fire at about 2:15 pm Monday.

The fire was mostly extinguished at 6:30 pm after local authorities dispatched 25 fire units and more than 100 fire engines to the scene. Helicopters were sent to rescue people trapped on the roof.

The cause of the fire remained unknown, but a witness said he saw construction materials burning before the fire climbed up the scaffolding and quickly spread.

Jing'an District government has arranged food and accommodations for fire-affected residents evacuated to nearby hotels.

Residents said the building, built in the 1990s, housed mainly teachers from several schools in Jing'an District, many of whom were retired.