The section of cliff that broke away is estimated at 60 metres wide by 15 metres long.
Rescuers used their bare hands to shift debris in a desperate bid to find victims while specially trained dog handlers have been deployed to try to locate survivors.
Sherine Tadros, Al Jazeera's correspondent in Cairo, said that a mass evacuation of the site and surrounding areas had been ordered because there was a risk that more rocks could slide down the face of the cliff.
"One of the main problems with the rescue effort now is that the houses are so densely packed that is very difficult for the heavy lifting equipment to get through the narrow streets and alleyways of this town," she said.
"The authorities also say that the heavy lifting equipment may spark further landslides."
Some estimates put the number of people
still missing at 500 [AFP]
Some people are resisting moving to the tents put in place by the government, Tadros reported.
"They don't trust the government will eventually re-house them," she said.
"They say they would rather risk the boulders than risk being homeless."
Tadros said the government had set up 2,000 emergency flats to house some families, but with many more made homeless by the rockslide this remains insufficient.
Al Jazeera's Lina Ghadban in Cairo said the fallen rocks and narrow streets were hampering the military in its rescue attempts.
"They have to do it delicately so they do not add to the destruction through the use of any heavy machinery that could bring down more rocks from the mountainside."
Hosni Mubarak, the Egyptian president, has ordered the government to provide housing for those left homeless and issue compensation to families of the victims, the state-owned Al-Ahram newspaper reported.
After an emergency meeting on Saturday evening, Ahmed Nazif, Egypt's prime minister, said that there would be a full review of housing settlements built throughout the country without construction permits, known as "ashwaeeyat".
|Police were deployed at the site to tackle grieving and angry residents calm [AFP]
Rescue work on Saturday was delayed because it took about five hours for cranes and special heavy lifting machinery to arrive before the grim task of removing rocks and rubble could begin.
Furious residents hurled stones and insults at authorities for "inefficient" rescue efforts on Sunday.
"It was horrible, like an earthquake," said Farghali Gharib, who lost eight members of his family - five sisters, a sister-in-law and her two children.
The reason for the rockfall was not immediately known, but residents said work had been taking place on the hill for several weeks and that the authorities had been warned about the dangers.
"They [authorities] were doing some work up on the hill. I am sure this is what caused the rockslide," Mohamed Gaber, a resident, said.
Mohamed al-Sayyed, 80, also blamed the authorities.
"They had said they would evacuate the entire neighbourhood in order to set up an industrial zone. We were happy about this ... but they did no such thing."
Abdel Latif Hossam, a driver, said: "There had already been some landslides, slightly hurting some people."
In 1994, a rockslide in the same area killed 30 people, but without any alternative housing, residents were forced to return.
Others said that the area where the disaster struck had been declared unsafe, but that alternative housing promised to them had been sold off.
September 6, 2008: Hundreds feared dead in Manshiyet Nasser rockslide
July 16, 2008: Train plows into cars in Marsa Matrouh, killing 40 people and injuring 50
July 12, 2008: Three-storey building in Nile Delta collapses killing five people including 7-year-old twins
January 1, 2008: Bus plunges into Nile killing 19 people
24 December, 2007: Twelve-storey building collapses in Alexandria killing 35 people
April 18, 2007: Head-on collision between school bus and truck kills 18 students
August 20, 2006: Nile Delta train collision kills 57 people
February 3, 2006: More than 1,000 passengers die after Egyptian ferry sinks en route to Saudi Arabia
The interior ministry said in a statement that plans were under way to evacuate the area in a month's time.
Most of the brick-built dwellings in the district have two floors and were put up without adhering to planning regulations and without construction permits.
The arid Moqattam hill is broken up by chalky rock slopes, and a number of unofficial housing areas are huddled at its base, along the length of a main road into the city.
Egypt has a poor track record of building safety, often blamed on the flouting of construction regulations.
Many houses have had extra floors added without permission.
In July, five people were killed, including seven-year-old twins, when a three-storey building in the Nile Delta collapsed, while last December 35 people were killed when a 12-storey building in Alexandria came down.
Two years earlier, in the same city, the collapse of a six-storey building killed 19 people. Three extra floors had been added illegally.
Tougher legislation against construction firms that ignore the law was introduced in 1996 after a building in Cairo's residential suburb of Heliopolis caved in, killing 64 people.
In a survey carried out by UN Habitat, a human settlement programme, Manshiyet Nasser is described as "the largest squatter, informal area in Cairo. There are 350,000 persons living in this area on about 850 acres with a gross residential density more than 400 persons per acre".
"The area is suffering from poor living qualities, inadequate services, lack of infrastructure, and deteriorated environmental conditions," the survey said.
There are more than 80 shantytowns in and around Cairo, housing millions of people with no legal basis.
In 2003, the housing ministry, under the auspices of the Suzanne Mubarak, the wife of the Egyptian president, launched a campaign to provide housing for some of the poorest Cairo residents, including those in the affected area.