MOTOZINTLA, Mexico, (CNN) -- President Ernesto Zedillo came face to face Saturday with distraught victims of the worst flooding to hit Mexico in 40 years and pledged help for hundreds of thousands of people stranded in villages that have been cut off from the rest of the world.

Zedillo visited some of the communities in the southern state of Chiapas hardest hit by a week of torrential rain that killed more than 100 people, left 20,000 homeless and 400,000 with no roads.

"I am married, and my two children and my wife are buried," Flavio Valesquez Vasquez, a middle-aged Indian, told Zedillo in the town of Motozintla.

"Our house collapsed. They have not found them," he added before breaking into tears and asking for a seat on a helicopter so he could return to his village to search for the bodies of his family. "They will help you," Zedillo promised.

In the town of Puerto Maderon, Reina Cecilia Fernandez, her husband and baby spent the night atop a wooden table on a neighbors' porch after they had to flee their home.

"We ran out with what we were wearing, and when we came back to check, everything was gone," she said.

Necessities in short supply

Heavy rain from a series of storms that swept up the coast over the past week have flooded huge tracts of Chiapas, turning roads into rivers, and hillsides into mud baths.

By Saturday, the downpours had made way for steaming sunshine, and roaring rivers had begun to slow. But dozens of communities remained cut off from help and were running short of vital supplies as the threat of disease mounted.

Miguel Valdez Galan, the government's emergency response director, said helicopters were fanning out across the Pacific coast, trying to rescue people who were still trapped on perilous islands of land near swollen rivers.

"We know what the damages are, and we have them prioritized," Valdez Galan said. He said it could take 15 to 20 days to restore land routes to some 60 towns and villages in Chiapas that have been cut off.

Many areas unreachable by roads

Emergency services collected 200 tons of supplies in Mexico City and flew them to Chiapas. But many areas, such as Tapachula, a city of 260,000, were unreachable by road, and the logistics of distributing aid were proving a nightmare, officials said.

"The equipment is arriving, but we face huge logistical problems," Zedillo told reporters on the road out of Motozintla. The road had washed out in many places and was cluttered with fallen logs.

"But I can say that today (Saturday) we are beginning to feel to some extent, after many days of national disaster, the first signs help is getting through. I'm sure that in the next two days, the people will start to feel some hope," Zedillo said.

But the mood in towns where whole neighborhoods had been swept away by flood waters and where muddy water still lapped against many window sills was one of anger and despair.

'They're not helping us'

Weeping women crowded around Zedillo as he walked.

"They're not helping us," 12-year-old Jacqueline Gutierrez de Leon said. "The river took away our house. I have nowhere to live."

Motozintla was being used as a base for relief efforts. On a makeshift airfield, helicopters came and went with a steady clatter while some of the 1,200 soldiers in the area formed human chains to load them with food, medicine and water.

Interior Minister Francisco Labastida said on Friday that the number of people swept to their deaths by raging rivers or buried in mudslides had risen to more than 100. He said 20,000 were homeless. Zedillo said 400,000 were cut off.

Navy Minister Jose Ramon Lorenzo Franco called the flooding the country's worst since a cyclone ripped through the city of Chetumal on the Yucatan peninsula in the 1950s.

The natural disaster was the latest setback for Chiapas' mainly impoverished and largely indigenous population.

The rains have moved further north along the Pacific coast, causing less severe flooding in the states of Oaxaca and Guerrero.

On Mexico's Gulf Coast, the states of Nuevo Leon and Tamaulipas were pounded by heavy rainfall caused by Tropical Storm Frances, which had caused severe flooding in the U.S. states of Texas and Louisiana.

Reuters contributed to this report.