PORT-AU-PRINCE, Haiti — Haitians are fleeing their quake-ravaged capital by the hundreds of thousands, aid officials said today, as their government promised to help nearly a half-million more move from squalid camps on curbsides and vacant lots into safer, cleaner tent cities.

Aid officials said some 200,000 people have crammed into buses, nearly swamped ferries and set out even on foot to escape the ruined capital. For those who stay, foreign engineers have started leveling land on the fringes of the city for tent cities, supposedly temporary, that are meant to house 400,000 people.

The goal is to halt the spread of disease at hundreds of impromptu settlements that have no water and no place for sewage. Homeless families have erected tarps and tents, cardboard and scrap as shelter from the sun, but they will be useless once the summer rainy season hits.

Rescue crews began abandoning hope of finding the final survivors of the magnitude-7.0 quake on Jan. 12. Thursday apparently was the first day since the earthquake that saw no successful rescues from the rubble.

Armies of foreign aid donors, instead, turned their attention to expanding their pipeline of food, water and medical care for survivors.

With extensive swaths of Port-au-Prince in ruins, more than 500 makeshift settlements with a population of about 472,000 are now scattered around the capital, said Jean-Philippe Chauzy, spokesman for the U.N.'s International Migration Institute.

The U.S. Army, Navy and Coast Guard are trying to patch up the Haitian capital's only functional industrial pier, which is key to getting in large aid shipments as well as to Haiti's long-term recovery.

Only four ships have been able to dock at the pier, where 15-inch-wide cracks make it risky to let more than one truck work at a time.