NEW DELHI (AP) — A dilapidated building and another under construction collapsed in India on Saturday, killing at least 15 people as rescuers searched for dozens of others feared trapped, police and fire officials said.

In New Delhi, a four-story 50-year-old structure toppled in an area inhabited by the poor. The collapse killed at least 11 people and one survivor was being treated in a hospital, said fire service officer Praveer Haldiar.

Indian rescuers gesture for an excavator to stop as they try to retrieve the body of a victim at the site of a building collapse in New Delhi, India, Saturday, June 28, 2014. A dilapidated building collapsed in the Indian capital on Saturday, killing at least seven people as rescuers searched for others believed to be trapped. (AP Photo/Altaf Qadri)

Hours later, a 12-story building under construction collapsed on the outskirts of Chennai, the capital of southern Tamil Nadu state, as heavy rains pounded the area.

Police said 17 construction workers had been pulled out so far and the search was continuing for nearly 30 others. Four of them died in a hospital, said police officer Mansur Ali.

Nearly 300 policemen and fire service workers were working through Saturday night, scouring the debris for survivors.

Indians watch rescuers work at the site of a building that collapsed in New Delhi, India, Saturday, June 28, 2014. A dilapidated building collapsed in the Indian capital on Saturday, killing at least seven people as rescuers searched for others believed to be trapped. (AP Photo/Altaf Qadri)

Most homes in the New Delhi area where the first building collapsed had been built without permission and using substandard materials, police officer Madhur Verma said.

The Press Trust of India news agency said the New Delhi collapse was triggered by construction work on an adjacent plot.

EDS NOTE: GRAPHIC CONTENT – Rescue workers carry the body of a victim amid the debris of a building that collapsed in New Delhi, India, Saturday, June 28, 2014. A dilapidated building collapsed in the Indian capital on Saturday, killing at least seven people as rescuers searched for others believed to be trapped. (AP Photo/Altaf Qadri)

Building collapses are common in India, where high demand for housing and lax regulations have encouraged some builders to cut corners, use substandard materials or add unauthorized extra floors.