PORT-AU-PRINCE, HAITI -- A massive aftershock jolted awake thousands of earthquake victims and relief workers in this ravaged capital early Wednesday, sparking new cries of fear and sorrow even as an enormous international aid effort continued to build.

The Navy hospital ship USNS Comfort drew near to Port-au-Prince Wednesday morning and received its first patients from the earthquake zone via helicopter, the Pentagon said. On Tuesday, hundreds of U.S. troops surged into the epicenter of the quake area to guard convoys and food distribution sites, while thousands more stationed themselves on ships and helicopters offshore to bolster relief and recovery efforts.

Many in the area were startled out of sleep just after 6 a.m. Wednesday by a tremor that measured 6.1 on the Richter scale -- one of the strongest aftershocks since the 7.0-magnitude quake crippled this city eight days ago.

Shrieks rose from the streets of Port-au-Prince as the quake -- apparently the first of any great significance in at least four days -- hit with a rolling, side-to-side motion that lasted several seconds. Less than 30 seconds later, a cascading roar could be heard across the city -- presumably the collapse of another building. Another cry went up toward the skies.

There was no overall assessment immediately available of new damage or casualties.

In Jacmel, the grassy field outside a convent shook like a children's carnival ride during the tremor, said to be centered about 35 miles outside Port-au-Prince. A thick fissure widened in the pale blue wall of the convent school, dark cement spilling out onto the walkway. People who had gathered at the convent grounds to sleep in what they thought was a safe place called out in fear, poking their heads out from under sheets strung up as tents among the purple flowers of trumpet vines. Children started to weep.

Many Haitians living on the streets since last Tuesday have received little or no food or medical assistance from their government or the international community. But there are increasing signs that the aid effort is gaining momentum.

Lt. Gen. Ken Keen, commander of the U.S. military operation in Haiti, said there are now roughly 2,000 troops on the ground and another 9,000 manning ships and helicopters. They have distributed 200,000 bottles of water and 600,000 rations. Crews are working to increase access to Haiti's damaged ports and better coordinate scores of military and relief flights that continue to ferry workers and supplies in and out of the earthquake zone.

"Every day we reach out further and touch the different pockets of the injured and the suffering," Keen said. "We are moving in the right direction, but this was a tragedy of epic proportion, and we have a long way to go in meeting the needs of the people."

As the U.N. Security Council approved 3,500 additional peacekeepers for the Haiti mission Tuesday, the U.S. military and other foreign forces began dropping food from planes, delivering troops by helicopter to volatile neighborhoods, and working to prepare other entry points for aid deliveries.

U.S. Navy divers arrived at Port-au-Prince's crippled port -- where a pier was perilously listing and two of three cranes were submerged -- to help engineers decide how much weight the docks could hold. Slowly, almost gingerly, they began to unload shipping containers from a barge that had sailed from Mobile, Ala., filled with supplies for the World Food Organization and Catholic Relief Services.

"It's really shaky down there," said one of the divers, Chris Lussier.

Defense Secretary Robert M. Gates signed orders Wednesday to dispatch a port-clearing ship equipped with cranes to Port-au-Prince, saying it could help get the port back in operation in a week or two, the Associated Press reported.

And the hospital ship Comfort, which sailed from Baltimore shortly after the quake struck, is due to dock off Port-au-Prince by mid-morning and will be able to give high-quality medical care to about 1,000 patients at a time. The patients will be transferred by helicopter from makeshift field hospitals, Keen said.

Even before the ship docked, the Pentagon said, a 6-year-old boy and 20-year-old man, both severely injured, were flown to there from the aircraft carrier USS Carl Vinson to receive more advanced medical treatment.

The delivery of aid is still hampered in some cases, leading to frustration among Haitians and the workers trying to help them. The medical organization Doctors Without Borders said in a statement Tuesday that another one of its cargo planes had been diverted from landing at the Port-au-Prince airport, where officials have struggled to cope with the massive influx of aid. The group said it has had five flights, with a total of 85 tons of medical supplies, refused landing so far.

Keen said planes are only turned away if the airport field is already crowded and they don't have sufficient fuel to be in a holding pattern. He also said that if the air traffic controller doesn't know what's on an incoming plane then he doesn't know what priority to give it.

"If the young airman has three planes coming in and he knows what's on one of them, he's going to land that one," Keen said. "He's working with the knowledge he has."

Haitian officials have made a request to have food, water and other aid delivered during the day. And U.S. military officials said they are working to improve their systems by putting a liaison officer in the process who would find out what's on the plane's cargo and communicate that to air traffic controllers.

Army Maj. Gen. Daniel Allyn said troops are working to open more airfields, get more trucks to help deliver water and supplies to victims, and bring in repair and construction equipment to start removing rubble. Some front-loaders could be seen beginning to scoop up the debris of several downtown buildings.

U.S. and Canadian military forces have been designated to guard food distribution sites as they open, freeing the U.N. security forces to patrol and keep order. The additional U.N. peacekeeping personnel approved Tuesday will bring the total in Haiti to 12,500.

Throughout the morning, U.S. Navy Black Hawk helicopters shuttled in troops from the Army's 82nd Airborne Division to the National Palace compound in the center of the city. The palace itself is in ruins, but the compound is fenced off and the troops appeared to be setting up a temporary camp.

Hundreds of Haitians, many of whom are living in a squalid tent city just outside the palace grounds, pressed against the iron bars to watch the troops arrive. An old man pushed around a wheelbarrow full of popcorn, selling small plastic bags of it.

"They've come here to help give this country direction again," said Josef Laurient, 35 and unemployed, as he watched the troops unload. "I'm so happy to see them, because up to now there has been no security for us."

On a grassy hilltop at the only golf course in Port-au-Prince, soldiers with the 82nd Airborne were unloading helicopters as they shuttled in boxes of emergency rations, which the troops distributed to the residents of a tent city that had grown around them. "It's all gone pretty smoothly. Everybody's been nice and calm," said Sgt. Caleb Barrieau.

U.S. troops had been dropping food and water from helicopters in various locations, but doing so had created mayhem as Haitians scrambled for the supplies. U.N. aid officials have advised against the practice after one drop near the slum of Cite Soleil almost caused a riot.

Keen said street violence has been hard to control in part because the Haitian police force has not located all of its officers. The day after the earthquake, 500 out of 9,000 policemen showed up, he said. Once food and water was distributed to them, the number shot up. By Wednesday, 2,000 had returned to work.

Among the many supplies running short in Haiti is blood, a World Health Organization official said Tuesday.

"One of the urgent health needs is for blood," said Jon K. Andrus, the deputy director of the WHO's Pan American Health Organization, which is based in Washington. "Haiti's National Blood Center building was damaged, and some equipment may need to be replaced."

Staff writers Susan Kinzie, Manuel Roig-Franzia, Mary Beth Sheridan and Scott Wilson in Port-au-Prince and staff writer Rob Stein in Washington contributed to this report.

http://www.washingtonpost.com/wp-dyn/content/article/2010/01/20/AR2010012000391_pf.html

© 2010 The Washington Post Company