Rescue crews searched for thousands of missing people in northwestern Pakistan Sunday as the death toll from massive flooding hit 1,100.

Officials say more than 27,000 people are still trapped by raging floodwaters caused by heavy monsoon rains that have pelted the region for days.

The rains eased a bit Sunday, allowing waters to recede slightly and officials to begin to survey the extent of the damage. Local officials said the flooding is the worst in decades in Khyber-Pakhtoonkhwa province.

"Aerial monitoring is being conducted, and it has shown that whole villages have washed away, animals have drowned and grain storages have washed away," said Latifur Rehman, spokesperson for the Provincial Disaster Management Authority. "The destruction is massive."

The United Nations estimates the flooding is affecting one million residents, meaning the death toll could climb much higher. Adnan Khan, a disaster management official, said about 700 people have drowned in the Peshawar Valley, and 115 others are missing.

More than 400 people have died in the Swat and Shangla districts. In Swat, the flooding has also destroyed more than 14,600 homes and nearly two dozen schools. More than 1,400 people also had to be rescued in Punjab province.

Rehman said 43 military helicopters and more than 100 boats have been deployed for the search-and-rescue operation. As many as 30,000 soldiers have also been called up to help.

"All efforts are being used to rescue people stuck in inaccessible areas and all possible help is being provided to affected people," Rehman said.

The government has opened displacement camps across the northwest, where officials fear waterborne diseases, such as diarrhea, cholera and skin problems, will spread.

As officials grapple with the magnitude of the disaster, aid organization mobilized to send food and water-filtration units to the region.

On Sunday, the United States government pledged $10 million in humanitarian assistance, including food packages and two water-filtration systems.

Flood victims also stepped up their criticism of the Pakistani government Sunday, saying they have seen little evidence of its assistance.

"The flood has devastated us all, and I don't know where my family has gone," said Hakimullah Khan, a resident of Charsadda who said his wife and three children are missing and the government has yet to offer help.

"Water is all around and there is no help in sight."

With files from The Associated Press