CANACONA, India - At least 15 workers were killed and many feared trapped when a half-built apartment block collapsed in the Indian resort state of Goa, police and media said on Sunday, the latest disaster to draw attention to safety standards amid a

construction boom.

Rescue workers at the site of the building collapse in Goa, India on Jan 5, 2014. [Photo/Xinhua]

The multi-storey building in Canacona, just over 4 km (two and a half miles) from the popular Palolem beach in the western state, collapsed on Saturday.

Senior police official O.P. Mishra said 15 workers were killed and 21 had been rescued so far. Some media reports put the death toll at 16.

Around 50 people were working at the site at the time and at least a dozen were still trapped under the concrete, according to witness accounts cited in media reports. One report put the number of people trapped as high as 60.

India's booming construction industry is set to be worth $1 trillion by 2025, which would make it the world's third largest, according to a report by Global Construction Perspectives and Oxford Economics.

But this dazzling growth has often come at the expense of safety standards.

At least 50 people were killed when a five-storey apartment block in India's financial centre, Mumbai, collapsed last September.

A collapse in April killed 72 people in Thane, a satellite city just outside Mumbai. Officials said the structure was built with poor materials and did not have proper approvals.

Goa police have registered a case - using a process known in India as a "first information report" - against the real estate development firm building the Goa block.

"Legal action will be taken against all who are responsible for this," Mishra said.