PANAJI, India (AP) – Rescuers using backhoes and shovels searched for survivors Sunday under a massive pile of broken concrete and dust that was left when a residential building under construction collapsed in southern India, killing at least 15 workers.

Authorities suspected dozens more may be trapped under the rubble, but were still trying to determine how many workers were on site when the five-story structure crumpled Saturday afternoon in the state of Goa. Witnesses reported seeing at least 40 workers.

Soldiers and firefighters listened for movement or cries from the wreckage as they worked overnight to clear the debris, state official Venancio Furtado said.

At least 10 people were pulled out alive overnight, but the chance of finding survivors was dwindling, Furtado said. By Sunday afternoon, the death toll had reached 15, according to the state government.

Goa Chief Minister Manohar Parrikar said he ordered a review of the construction project, after seeing cracks that developed in the adjacent apartment building constructed by the same company, Mumbai-based Bharat Developers and Realtors Pvt. Ltd.

``The design is faulty, which is why the tragedy happened,'' Parrikar said.

Police began investigating both the building company and city officials who approved the construction on a patch of marshland in Canacona, about 70 kilometers (44 miles) from the state capital of Panaji. But they have been unable to track down the construction manager and building contractor.

``Without the contractor, it is impossible for us to know how many laborers were on the shift,'' said state official Ajit Panchwadkar, who was supervising the rescue effort Sunday.

Many of the workers had come from other, poorer states, including Jharkhand, Bihar and Uttar Pradesh, in search of jobs in India's thriving construction business. One worker who was not at the scene when the building collapsed said he earned about 300 rupees ($4.80) for a day's work, according to Press Trust of India.

Several workers took the day off Saturday to attend a nearby state cultural fair.

``We rushed from the event when we heard that the building had fallen,'' said Manoj Kumar, a worker originally from the eastern state of Orissa.

Building collapses are common in India, as massive demand for housing and lax regulations often encourage builders to cut corners by using substandard materials or add unauthorized extra floors.