MUMBAI, India -- Police arrested two builders as rescue workers on Saturday finished a two-day search for survivors in the collapse of a residential building being constructed illegally in India's financial capital. At least 72 people were killed in the accident, the worst house collapse in the country in recent decades.

Another 70 people were injured when the eight-story building on forest land in the Mumbai suburb of Thane caved in into a mound of steel and concrete Thursday evening, police said. The dead included 17 children.

Thirty-six of the injured were still in city hospitals and the rest were discharged after medical treatment, said Sandeep Malvi, a spokesman for the local municipality.

Local police commissioner K.P. Raghuvanshi said two builders were taken into custody and would be formally charged after an investigation.

Police on Friday registered a case of culpable homicide against the builders, Salil, who uses one name, and Khalil Jamadar, the Press Trust of India news agency said. If convicted, they can be sentenced up to life in prison.

Rescue workers with sledgehammers, chainsaws and hydraulic jacks worked through Friday night to break through the tower of rubble in their search for survivors, police officer Dahi Phale said. Six bulldozers were brought to the scene.

Twenty bodies were recovered overnight and the rescue work ended at noon Saturday after 42 hours, Malvi said.

Prithviraj Chavan, the top elected official of Maharashtra state, said that a government probe had been ordered into the accident, and that a deputy municipal commissioner and a senior police officer had been suspended for dereliction of duty.

At the time of the collapse, between 100 and 150 people were in the building. Many were residents or construction workers who were living at the site as they worked on it, Malvi said.

A nearby hospital was filled with the injured, many of whom had head wounds, fractures and spinal injuries. Hospital officials searched in vain for the parents of an injured 10-month-old girl who was rescued after 12 hours.

Police said rescue workers saved 56 people from the wreckage, including a woman who was rescued 36 hours after the accident.

At least four floors of the building had been completed and were occupied. Workers had finished three more floors and were adding the eighth when it collapsed, police Inspector Digamber Jangale said.

It was not immediately clear what caused the structure to collapse, but Raghuvanshi said it was weakly built

Police with rescue dogs searched the building, which appeared to have buckled and collapsed on itself.

Building collapses are common in India as builders try to cut corners by using substandard materials, and as multi-storied structures are built with inadequate supervision. The massive demand for housing around India's cities and pervasive corruption often result in builders adding unauthorized floors or putting up illegal buildings.

The neighborhood where the building collapsed was part of a belt of more than 2,000 illegal structures that had sprung up in the area in recent years, said Malvi, the municipal spokesman.

"Notices have been served several times for such illegal construction," he said. "Sometimes notices are sent 10 times for the same building."

The building that collapsed was illegally constructed on forest land, and the city informed forestry officials twice about it, Malvi said.

In one of the worst recent collapses in India, 67 people were killed in November 2010 when an apartment building in a congested New Delhi neighborhood crumpled. That building was two floors higher than legally allowed.

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