"We were able to save him, but he may lose his leg," Awasthi said.
The building, which housed workers for Mumbai's municipal government, was constructed in 1980, Awasthi said, adding they still did not know what caused it to fall down.
But local residents complained of substandard materials and corruption as the root causes of such disasters.
Some neighbours said they even feared about the safety of their own buildings.
"We can't know that tomorrow it won't be our turn," said Anupama Shivalkar, who lives in a nearby apartment block.
Two other buildings have fallen down in Mumbai this year.
In April, at least 72 people died when an illegally constructed building fell. Two months later, a three-story structure collapsed, killing at least 10 people, including five children.
- AP