NEW DELHI — Anna Halder sat on a patch of packed mud and dialed her cell phone Tuesday, clinging to the hope that her parents or sisters somehow survived under the wreckage of their collapsed apartment building and would pick up.

“It’s ringing,” she said. No one answered. She dialed again.

At least 66 people were killed and 73 were injured after the crude brick building crashed down in a congested New Delhi neighborhood. By Tuesday evening, as rescue workers continued to tear through the pile of broken bricks, twisted iron rods and concrete slabs, hope for finding more survivors was fading.

The building collapsed Monday about the time families were cooking dinner. Halder, 18, had not yet returned from her job as a housekeeper. Her working-class family, like millions of other migrants, moved to New Delhi hoping to get jobs in the growing Indian capital.

They, and many others from West Bengal, found housing in the crude brick building in the Lalita Park neighborhood near the Yamuna River because it was one of the rare homes they could afford amid the skyrocketing real estate prices in the crowded city.

But the building was two floors higher than legally allowed, and its foundation appeared to have been weakened by water damage following monsoon rains. The soil near the river is too weak to support such tall buildings, New Delhi Lt. Gov. Tejendra Khanna said.

Poor construction material and inadequate foundations often are blamed for building collapses in India. In New Delhi, where land is at a premium, unscrupulous builders often break building laws to add additional floors to existing structures.

While the collapse was still being investigated, New Delhi’s top elected official blamed poor construction and maintenance and vowed to punish those who had allowed the extra floors to be built.

“The scale of the tragedy is unprecedented,” Sheila Dikshit said.

The building’s owner, Amrit Singh, was arrested Tuesday evening after fleeing the area, the Press Trust of India reported. Officials evacuated another of Singh’s buildings next door, after finding its basement was also flooded.

When the building fell, residents said they heard a rumble like thunder. They ran to the site and tried to reach those inside by digging with their hands before police and rescue teams arrived.

“There were so many dead bodies, there was no movement at all,” said Dil Nawaz Ahmed, a 25-year-old journalist who lives nearby. He said he managed to help free five injured residents, but mainly pulled out bodies, which he carried to waiting ambulances. “There were many women and children.”

Rescuers sawed through iron rods and shifted concrete with a bulldozer. Sniffer dogs searched out people. Ambulances parked nearby at the ready. Women crying over lost loved ones were led away.

Malti Halder was still waiting for information about her husband and daughter. She was not related to Anna Halder; the name is common in West Bengal where many of the residents are from.

“I did not find them at the hospital. I’ve been searching for them since last night but have not found them,” she said.

M.D. Shahanawaz, a 23-year-old student, teared up as his hopes for a friend who lived in the building dwindled.

“He’s dead,” he said. “Everybody is coming out critical or dead.”

Dozens of black-and-white photographs of the dead hung on the wall outside a mortuary so relatives and friends could identify the bodies of their loved ones.