Two held over building collapse in India that claimed lives of 20

It was one of two weekend building collapses that killed at least 20 people

Rescue workers conduct a search operation for survivors at the site of a collapsed 11-storey building that was under construction on the outskirts of the southern Indian city of Chennai (REUTERS)

Police in India detained two construction company directors as rescuers searched for workers believed buried in the rubble of a building that collapsed during monsoon rains.

It was one of two weekend building collapses that killed at least 20 people.

The 12-storey apartment structure the workers were building collapsed late yesterday while heavy rains and lightning were pounding the outskirts of Chennai, the capital of Tamil Nadu state.

Police said 28 construction workers had been pulled out so far and the search was continuing for more than a dozen others.

Four of the workers died on the spot and another five succumbed to injuries later in a hospital, said police officer George Fernandes.

Thirteen injured workers are being treated in hospital, while six others were allowed to go home after medical attention, he said.

Police officer Kanan said two directors of the construction company, Prime Sristi, have been detained for questioning as authorities began investigating the cause of the collapse. The officer uses only one name.

Balaguru, one of the builders, said the structure collapsed possibly due to the impact of lightning.

"Usually, once the construction gets over we install the equipment to prevent the building from a thunder strike. It was nearing completion," the Press Trust of India news agency quoted Balaguru, who uses one name, as saying.

Nearly 300 policemen and fire service workers worked overnight, looking for survivors in the debris. They used gas cutters, iron rods and shovels to reach those trapped in the rubble.

Earlier yesterday, a four-storey, 50-year-old structure toppled in an area of New Delhi inhabited by the poor.

Eleven people died and one survivor was being treated in a hospital, said fire service officer Praveer Haldiar.

Most homes in that part of the capital were 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.

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 unauthorised extra floors.

In April last year, 74 people were killed when an eight-storey building being constructed illegally in the Mumbai suburb of Thane in western Maharashtra state caved in. It was the worst building collapse in the country in decades.

PA