Indian authorities say a low-rise building has collapsed in Delhi's walled old city, killing at least five people and injuring more than 20 others.

Officials say construction work at an adjacent site likely triggered the building's collapse, which happened late Tuesday. Rescuers were trying to reach at least 20 people feared trapped in the rubble.

Delhi Mayor Rajni Abbi promised an investigation into the incident. Many Indian buildings and construction projects do not conform to safety regulations.

In November last year, a five-story residential building collapsed in the Indian capital, killing at least 60 people.