A rescue worker carries an injured girl at the site of a building collapse in New Delhi November 16, 2010. A residential building collapsed in Lalita Park in New Delhi's Laxmi Nagar area on Monday evening. [Photo/Agencies] NEW DELHI- Rescuers hammered slabs of concrete and dug with their hands Tuesday to pull survivors and bodies from a four-story apartment building that collapsed into a mountain of rubble in a poor New Delhi neighborhood. At least 64 people were killed and scores injured. The 15-year-old building housing about 200 people _ mostly migrant workers and their families _ collapsed Monday evening in New Delhi's congested Lalita Park area, where emergency efforts were hampered because vehicles had difficulty navigating its narrow alleyways. "The scale of the tragedy is unprecedented," New Delhi's top elected official, Sheila Dikshit, said as she toured the site. An 18-year-old man named Niranjan was walking home from the park when he saw the building come crashing down with his family inside. "The entire building collapsed within seconds as if it was made of sand," he told Press Trust of India. "I ran toward the rubble, but there was nothing I could do." His brother, mother, sister-in-law and niece were all found dead, he said. The cause of the collapse was not immediately clear. One official said the building may have been weakened by water damage following monsoon rains; Residents said the landlord was illegally constructing an additional floor on the building. Officials ordered the evacuation of at least one other nearby building that they feared could collapse too, Dikshit said. Police said they had filed charges against Amrit Singh, the owner of the building, and a search was on to locate him. Residents said he fled the area right after the building collapsed. Neighbors, who were the first to arrive at the accident site, used their bare hands to dig into the piles of concrete, bricks and mortar, until they were joined by police and firefighters, who used jackhammers to cut through the iron rods jutting from the wreckage. Police brought in sniffer dogs to locate people trapped under the debris. Many rescuers were still working with sledgehammers and their hands Tuesday to remove the rubble stone by stone and pull out bodies as neighbors watched from nearby rooftops. At one point, the rescuers uncovered the body of a small child. One woman whose granddaughter was killed wailed in grief from a nearby roof. By Tuesday afternoon, at least 64 bodies were recovered and another 80 people were injured, city police official Mohammed Akhlaq said. Lalita Park is a congested neighborhood near the banks of the Yamuna River that houses some of the millions of impoverished workers who stream into New Delhi from rural villages hoping to get jobs in the growing Indian capital. "A large number of people come to Delhi in search of jobs. This was cheap accommodation for a lot of them," said Deep Mathur, a city official. 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. Dikshit blamed the builder for the poor construction and maintenance of the building and said the government would probe whether he had the necessary permits to add floors. Yoginder Chandolia, another city official, said water from this season's unusually heavy monsoon rains _ which forced the Yamuna to overflow its banks _ had sent water cascading into the basement of the building. "During the recent flood, water reached the building's foundation and weakened it considerably, resulting in the collapse," he said. Residents were angry that police and firefighters took so long to arrive after the building collapsed about 8:15 p.m. Monday. "They took more than 45 minutes to reach the site. And then there was confusion about how they were going to bring in the ambulances," said resident Mohinder Singh. But municipal officials said they had enormous problems navigating the narrow alleyways. "Our biggest hurdle was to get vehicles through. Even ambulances got stuck," said Mathur.