(CNN) -- The day after an 8.0-magnitude earthquake shook southern Peru, killing at least 400 people and injuring 1,500, residents of one hard-hit city yelled "Help us! Help us!" as President Alan Garcia toured the area.
Garcia, who traveled the 260 kilometers (160 miles) southeast of Lima in a helicopter Thursday, said arrangements were being made to get water and food into Pisco.
"Since the highway is shut, it doesn't permit help at this time," Garcia said, adding that efforts were under way to re-establish downed bridges so that trucks bearing aid could reach the city.
Shortly afterward, a spokesman for the Peruvian Embassy in Washington said supplies had already begun to flow toward Pisco from the south.
Garcia said one of the priorities was ordering at least 150 coffins. More than 200 people died in Pisco, and almost 70 percent of the city of 68,000 residents was destroyed, Minister of Health Carlos Vallejos told Andina television.
"There aren't any buildings that are in good condition. Even the very modern buildings around the central plaza are totally destroyed," Vallejos said, calling Pisco a city in crisis.
"They're still looking for more victims because entire buildings have collapsed. The situation is very, very serious. There's no electricity, there's no water, telephone service is very limited, there are no stores," he said.
An America TV Peru reporter said she could see no sign of police to quell looting.
Several health centers in Pisco were so damaged they could not operate, said Dan Epstein, a spokesman for the Pan American Health Organization, based in Washington.
People searched for missing relatives amid the wreckage of a church that collapsed Wednesday night as services were being held. Several children wandered aimlessly. "Oh, my God, who do these little children belong to?" Garcia asked.
Peru's civil defense put the total death toll from the quake at 400. But the deputy emergency relief coordinator for the United Nations, Margareta Wahlstrvm, said 450 people were killed. In addition, almost 400 houses were destroyed, she said.
The American Embassy in Lima confirmed that at least one American was among the dead, U.S. State Department spokesman Sean McCormack said. The embassy is trying to find and help U.S. citizens in Peru.
Sheet-covered bodies lined a street in Chincha near the country's southern coast.
Hundreds of people were injured in Ica farther south, reported journalist Guillermo Galdos in an interview with ITN. The morgue collapsed, and the International Red Cross has sent body bags to the city, Galdos said.
"The police and military have been sent; they've seen quite a lot of looting," Galdos said.
The two-minute, 8.0-magnitude quake struck Wednesday evening, and strong aftershocks followed, including a 6.0-magnitude temblor on Thursday, according to the
U.S. Geological Survey.
Garcia declared a state of emergency, including Ica, Chincha and Canete among the other places hardest hit.
Telephone lines were down in a number of cities, and television stations were pleading for viewers to limit cell phone calls so that the lines would be open for emergency use.
Dr. Rubio Luis, director of the Hospital de la Solidaridad in
Lima, told Panamericana TV that he had heard many injured people -- rather than seeking medical treatment -- remained at home to protect their valuables from theft.
Luis said most of the injuries included broken bones and fractures. He said he was worried that city water pipes may have broken in the earthquake. If people drink polluted water, he fears an outbreak of intestinal sickness.
The earthquake was more powerful than its initial measurements suggested. The U.S. Geological Survey upgraded it Thursday from 7.9 to 8.0.
When the shaking had stopped, a major highway along the coast was nearly destroyed, said Giorgio Ferrario, head of the Peruvian International Federation of the Red Cross and Red Crescent. Rescuers have been severely hampered by fallen debris, he said.
"It took them seven hours -- seven hours and a half to do normally what is done in two hours and a half because of the road," Ferrario said. "The information gathered from the field is that destruction is extensive."
Towns affected by the quake are old, Ferrario said, and communities are spread out, making communication more difficult.
National civil defense authorities unloaded two planes that flew from Panama with tents and blankets, and Ferrario said he hoped volunteers could begin distributing the supplies Thursday afternoon.
Fernando Calderon, a visiting American who sent photos of the aftermath to CNN's I-Report, said it was chaotic immediately after the earthquake.
"Everybody started crying -- kids, everybody," Calderon said. "Everybody started running toward any empty space. Everybody was afraid the buildings were going to collapse."
The government has closed schools, said Labor Minister Susana Pinilla Cisneros, who announced that Lima's Labor Ministry and other public buildings had sustained damage.
The quake struck at 6:41 p.m. (7:41 p.m. ET) and was centered 25 miles (40 kilometers) west-northwest of Chincha Alta and 90 miles (145 kilometers) south-southeast of Lima, according to the U.S. Geological Survey. The epicenter was 25 miles (40 kilometers) below the Earth's surface.
The major quake prompted a tsunami warning, issued by the Pacific Tsunami Warning Center, which was eventually canceled.
A tsunami was generated by the quake, but it was not large enough to damage the Central or South American coast, said Gerard Fryer with the Pacific Tsunami Warning Center.
More than 11 smaller earthquakes occurred in the hours following the original temblor -- most a few miles from its epicenter, but some also in central Peru. Their magnitudes ranged from 5.0 to 6.3.
Peru, and most of the South American Pacific coast, are on the border of two tectonic plates. The South American plate sits beneath the entire continent and extends across the Atlantic about halfway to Africa. The Nazca plate extends across the Pacific along most of the coast.